The invention claimed is:1. A method for receiving a paging message, the method comprising:receiving, by a User Equipment (UE), system information sent by an evolved Node B (eNB), wherein the system information carries information about carriers on which the paging message is allowed to be received;determining, by the UE, a paging carrier according to the information about the carriers on which the paging message is allowed to be received, and a preset rule, wherein the paging carrier is a primary carrier or a secondary carrier of the eNB; andreceiving, by the UE, the paging message sent by the eNB on the paging carrier;wherein determining, by the UE, the paging carrier according to the information about the carriers on which the paging message is allowed to be received, and the preset rule comprises:determining, by the UE, the paging carrier in the equation of PC=floor (UE_ID/(N*Ns)) mod Nc, wherein PC represents an index corresponding to the paging carrier; N represents min (T, nB), wherein nB represents a paging density, and T represents the default paging periodicity; Ns represents max (1, nB/T); Nc represents a total number of paging carriers comprising a total number of primary and secondary carriers on which the paging message is allowed to be sent and UE_ID is determined according to the identifier of the UE; ordetermining, by the UE, a paging-carrier initial judgment variable in the equation of PCint=floor(UE_ID/nBmin) mod (nBall/nBmin), and to determining the paging carrier according to the paging-carrier initial judgment variable, wherein the paging-carrier initial judgment variable and the paging carrier satisfy the following constraint condition:when PCint<(nB0)/nBmin, PCindex is 0; andwhen (Σi=0PCindex-1nBi)/nBmin<=PCint<(Σi=0PCindexnBi)/nBmin, a corresponding value of PCindex is i, wherein i is an integer, and i>=1;wherein PCint represents the paging-carrier initial judgment variable, PCindex represents the index of the paging carrier, nB represents a paging density, nBranchor represents the paging density of the primary carrier, nBnon-anchor represents the paging density of a secondary carrier, nBmin=min(nBanchor, nBnon-anchor), nBall=nBanchor+nBnon-anchor, nBi represents the paging density of a carrier with an index i, wherein i=0, 1, . . . , nBall?1, nB0 represents the paging density of the primary carrier, and UE_ID is determined according to the identifier of the UE.2. The method according to claim 1, wherein the information about the carriers on which the paging message is allowed to be received comprises at least one of:downlink operating frequencies of the carriers;uplink operating frequencies of the carriers;information characterizing the indexes of the carriers;a bitmap configuration of available downlink sub-frames;a configuration of downlink timeslots;in-band carrier information;a paging density or densities of the primary carrier or the secondary carriers;a default paging periodicity of the primary carrier or the secondary carriers; ora quantity of primary and secondary carriers on which the paging message is allowed to be received.3. The method according to claim 1, wherein receiving, by the UE, the paging message sent by the eNB on the paging carrier comprises:residing, by the UE, on the paging carrier, and receiving the paging message sent by the UE on the paging carrier; orif the paging carrier is not the primary carrier of the eNB, residing, by the UE, on the primary carrier of the eNB, and receiving the paging message sent by the UE on the paging carrier at a paging instance of time of the paging carrier.4. The method according to claim 1, wherein the method further comprises:if the paging carrier is a secondary carrier, listening, by the UE, to system information update notification sent on the secondary carrier, and receiving updated system information on the primary carrier upon reception of the notification.5. A method for sending a paging message, the method comprising:broadcasting, by an evolved Node B (eNB), system information, wherein the system information carries information about carriers on which the paging message is allowed to be received; andsending, by the eNB, the paging message on a carrier on which the paging message is allowed to be received, so that the paging message is received by a user equipment, UE on a paging carrier, wherein the carrier on which the paging message is allowed to be received is a primary carrier or a secondary carrier, and the paging carrier is determined by the UE according to the information about the carriers on which the paging message is allowed to be received and the preset rule;wherein:the paging carrier is determined by the UE in the equation of PC=floor (UE_ID/(N*Ns)) mod Nc, wherein PC represents an index corresponding to the paging carrier; N represents min (T, nB), wherein nB represents a paging density, and T represents the default paging periodicity; Ns represents max (1, nB/T); Nc represents a total number of paging carriers comprising a total number of primary and secondary carriers on which a paging message is allowed to be sent and UE_ID is determined according to the identifier of the UE, orthe paging carrier is determined by the UE according to a paging-carrier initial judgment variable, wherein the paging-carrier initial judgment variable in the equation of PCint=floor(UE_ID/nBmin) mod (nBall/nBmin), and the paging-carrier initial judgment variable and the paging carrier satisfy the following constraint condition:when PCint<(nB0)/nBmin, PCindex is 0; andwhen (Σi=0PCindex-1nBi)/nBmin<=PCint<(Σi=0PCindexnBi)/nBmin, a corresponding value of PCindex is i, wherein i is an integer, and i>=1;wherein PCint represents the paging-carrier initial judgment variable, PCindex represents the index of the paging carrier, nB represents a paging density, nBranchor represents the paging density of the primary carrier, nBnon-anchor represents the paging density of a secondary carrier, nBmin=min(nBanchor, nBnon-anchor), nBall=nBanchor+nBnon-anchor, nBi represents the paging density of a carrier with an index i, wherein i=0, 1, . . . , nBall?1, nB0 represents the paging density of the primary carrier, and UE_ID is determined according to the identifier of the UE.6. The method according to claim 5, wherein the information about the carriers on which the paging message is allowed to be received comprises at least one of:downlink operating frequencies of the carriers;uplink operating frequencies of the carriers;information characterizing the indexes of the carriers;a bitmap configuration of available downlink sub-frames;a configuration of downlink timeslots;in-band carrier information;a paging density or densities of the primary carrier or the secondary carriers;a default paging periodicity of the primary carrier or the secondary carriers; ora quantity of primary and secondary carriers on which the paging message is allowed to be received.7. The method according to claim 5, further comprises:sending, by the eNB, a system information update notification on the carrier on which the paging message is allowed to be received, when the system information is updated.8. The method according to claim 5, further comprises:obtaining, by the eNB, information about whether the UE supports a capability to receive the paging message on the secondary carrier, and notifying a Mobility Management Entity (MME) of the information about whether the capability to receive the paging message on the secondary carrier is supported.9. The method according to claim 5, wherein before the eNB sends the paging message on the carrier on which the paging message is allowed to be received, the method further comprises:receiving, by the eNB, information notified by a Mobility Management Entity (MME) about whether a UE supports a capability to receive the paging message on the secondary carrier, and determining whether the UE supports a capability to receive the paging message on the secondary carrier.10. A User Equipment (UE), comprising: a processor, a memory, and a transceiver, wherein the transceiver receives and transmits data under the control of the processor, the memory stores preset program, and the processor reads and executes the program in the memory:to receive system information sent by an evolved Node B (eNB) through the transceiver, wherein the system information carries information about carriers on which a paging message is allowed to be received;to determine a paging carrier according to the information about the carriers on which the paging message is allowed to be received, and a preset rule, wherein the paging carrier is a primary carrier or a secondary carrier of the eNB; andto receive the paging message sent by the eNB on the paging carrier through the transceiver;the processor further reads and executes the program in the memory;to determine, by the UE, the paging carrier in the equation of PC=floor (UE_ID/(N*Ns)) mod Nc, wherein PC represents an index corresponding to the paging carrier; N represents min (T, nB), wherein nB represents a paging density, and T represents the default paging periodicity; Ns represents max (1, nB/T); Nc represents a total number of paging carriers comprising a total number of primary and secondary carriers on which the paging message is allowed to be sent and UE_ID is determined according to the identifier of the UE; orto determine, by the UE, a paging-carrier initial judgment variable in the equation of PCint=floor(UE_ID/nBmin) mod (nBall/nBmin), and to determining the paging carrier according to the paging-carrier initial judgment variable, wherein the paging-carrier initial judgment variable and the paging carrier satisfy the following constraint condition:when PCint<(nB0)/nBmin, PCindex is 0; andwhen (Σi=0PCindex-1nBi)/nBmin<=PCint<(Σi=0PCindexnBi)/nBmin, a corresponding value of PCindex is i, wherein i is an integer, and i>=1;wherein PCint represents the paging-carrier initial judgment variable, PCindex represents the index of the paging carrier, nB represents a paging density, nBranchor represents the paging density of the primary carrier, nBnon-anchor represents the paging density of a secondary carrier, nBmin=min(nBanchor, nBnon-anchor), nBall=nBanchor+nBnon-anchor, nBi represents the paging density of a carrier with an index i, wherein i=0, 1, . . . , nBall?1, nB0 represents the paging density of the primary carrier, and UE_ID is determined according to the identifier of the UE.11. The UE according to claim 10, wherein the information about the carriers on which the paging message is allowed to be received comprises at least one of:downlink operating frequencies of the carriers;uplink operating frequencies of the carriers;information characterizing the indexes of the carriers;a bitmap configuration of available downlink sub-frames;a configuration of downlink timeslots;in-band carrier information;the paging density or densities of the primary carrier or the secondary carriers;a default paging periodicity of the primary carrier or the secondary carriers; ora quantity of primary and secondary carriers on which the paging message is allowed to be received.12. The UE according to claim 10, wherein the processor reads and executes the program in the memory:to reside on the paging carrier, and to receive the paging message sent by the UE on the paging carrier.13. The UE according to claim 10, wherein the processor reads and executes the program in the memory:if the paging carrier is not the primary carrier of the eNB, to reside on the primary carrier of the eNB, and to receive the paging message sent by the UE on the paging carrier at a paging instance of time of the paging carrier;if the paging carrier is a secondary carrier, to listen to system information update notification sent on the secondary carrier, and to receive updated system information on the primary carrier upon reception of the notification.14. An evolved Node B (eNB), comprising: a processor, a memory, and a transceiver, wherein the transceiver receives and transmits data under the control of the processor, the memory stores preset program, and the processor reads and executes the program in the memory:to broadcast system information through the transceiver, wherein the system information carries information about carriers on which a paging message is allowed to be received; andto instruct the transceiver to send the paging message on a carrier on which the paging message is allowed to be received, so that the paging message is received by a user equipment, UE on a paging carrier, wherein the carrier on which the paging message is allowed to be received is a primary carrier or a secondary carrier, and the paging carrier is determined by the UE according to the information about the carriers on which the paging message is allowed to be received and the preset rule;wherein:the paging carrier is determined by the UE in the equation of PC=floor (UE_ID/(N*Ns)) mod Nc, wherein PC represents an index corresponding to the paging carrier; N represents min (T, nB), wherein nB represents a paging density, and T represents the default paging periodicity; Ns represents max (1, nB/T); Nc represents a total number of paging carriers comprising a total number of primary and secondary carriers on which a paging message is allowed to be sent and UE_ID is determined according to the identifier of the UE, orthe paging carrier is determined by the UE according to a paging-carrier initial judgment variable, wherein the paging-carrier initial judgment variable in the equation of PCint=floor(UE_ID/nBmin) mod (nBall/nBmin), and the paging-carrier initial judgment variable and the paging carrier satisfy the following constraint condition:when PCint<(nB0)/nBmin, PCindex is 0; andwhen (Σi=0PCindex-1nBi)/nBmin<=PCint<(Σi=0PCindexnBi)/nBmin, a corresponding value of PCindex is i, wherein i is an integer, and i>=1;wherein PCint represents the paging-carrier initial judgment variable, PCindex represents the index of the paging carrier, nB represents a paging density, nBranchor represents the paging density of the primary carrier, nBnon-anchor represents the paging density of a secondary carrier, nBmin=min(nBanchor, nBnon-anchor), nBall=nBanchor+nBnon-anchor, nBi represents the paging density of a carrier with an index i, wherein i=0, 1, . . . , nBall?1, nB0 represents the paging density of the primary carrier, and UE_ID is determined according to the identifier of the UE.15. The eNB according to claim 14, wherein the information about the carriers on which the paging message is allowed to be received comprises at least one of:downlink operating frequencies of the carriers;uplink operating frequencies of the carriers;information characterizing the indexes of the carriers;a bitmap configuration of available downlink sub-frames;a configuration of downlink timeslots;in-band carrier information;a paging density or densities of the primary carrier or the secondary carriers;a default paging periodicity of the primary carrier or the secondary carriers; ora quantity of primary and secondary carriers on which the paging message is allowed to be received.16. The eNB according to claim 14, wherein the processor reads and executes the program in the memory:to send a system information update notification on the carrier on which the paging message is allowed to be received, when the system information is updated.17. The eNB according to claim 14, wherein the processor reads and executes the program in the memory:to obtain information about whether a UE supports a capability to receive the paging message on a secondary carrier, and to notify a Mobility Management Entity (MME) of the information about whether the capability to receive the paging message on a secondary carrier is supported.18. The eNB according to claim 14, wherein the processor reads and executes the program in the memory:before sending the paging message on the carrier on which the paging message is allowed to be received, to receive information notified by a Mobility Management Entity (MME) about whether the UE supports a capability to receive the paging message on a secondary carrier, and to determine whether the UE supports a capability to receive the paging message on a secondary carrier.