What is claimed is:1. A method for wireless communication, the method comprising:obtaining access stratum context identifier information of a first terminal device, wherein the access stratum context identifier information of the first terminal device is used to identify access stratum context information of the first terminal device that is related to the first terminal device on a first access network device; anddetermining the first access network device according to the access stratum context identifier information of the first terminal device, so that a second access network device providing a network service to the first terminal device obtains the access stratum context information of the first terminal device from the first access network device, wherein determining the first access network device according to the access stratum context identifier information of the first terminal device comprises:determining the first access network device according to the access stratum context identifier information of the first terminal device and a first mapping relationship, wherein the first mapping relationship is a mapping relationship between access stratum context identifier information of at least one terminal device and an identifier of at least one access network device, and the at least one terminal device comprises the first terminal device.2. The method according to claim 1, wherein a number or a bit stream that is in the access stratum context identifier information of the first terminal device and that is used to identify information about the first access network device is different from a number or a bit stream of an identifier of the first access network device.3. The method according to claim 1, wherein the first mapping relationship is a one-to-one mapping relationship between at least one piece of access stratum context identifier information and the identifier of the at least one access network device, and the at least one piece of access stratum context identifier information comprises the access stratum context identifier information of the first terminal device.4. The method according to claim 1, wherein the first mapping relationship is a one-to-one mapping relationship between at least one piece of number segment information and the identifier of the at least one access network device, and the at least one piece of number segment information comprises number segment information of the access stratum context identifier information of the first terminal device.5. The method according to claim 1, wherein the first mapping relationship is preconfigured in the at least one access network device, and the at least one access network device comprises the second access network device.6. The method according to claim 1, wherein the first mapping relationship is preconfigured in a network node dedicated for parsing the access stratum context identifier information to obtain an identifier of an access network device.7. The method according to claim 1, wherein the access stratum context identifier information of the first terminal device is pre-allocated by the first access network device to the first terminal device.8. A device for wireless communication, the device comprising:an obtaining unit, configured to obtain access stratum context identifier information of a first terminal device, wherein the access stratum context identifier information is used to identify access stratum context information of the first terminal device that is related to the first terminal device on a first access network device; anda sending unit, configured to send the access stratum context identifier information to a second access network device providing a network service to the first terminal device, so that the second access network device obtains the access stratum context information from the first access network device corresponding to the access stratum context identifier information, wherein the first access network device is determined according to the access stratum context identifier information of the first terminal device and a first mapping relationship, wherein the first mapping relationship is a mapping relationship between access stratum context identifier information of at least one terminal device and an identifier of at least one access network device, and the at least one terminal device comprises the first terminal device.9. The device according to claim 8, wherein a number or a bit stream that is in the access stratum context identifier information of the first terminal device and that is used to identify information about the first access network device is different from a number or a bit stream of an identifier of the first access network device.10. The device according to claim 8, wherein there is a mapping relationship between number segment information of the access stratum context identifier and an identifier of the first access network device.11. The device according to claim 8, wherein the access stratum context identifier information of the first terminal device is pre-allocated by the first access network device to the first terminal device.12. The device according to claim 8, wherein sending the access stratum context identifier information to a second access network device providing a network service to the first terminal device comprises:sending an RRC resume request message to the second access network device, wherein the RRC resume request message carries the access stratum context identifier information.13. A device for wireless communication, wherein the device comprises:an obtaining unit, configured to obtain access stratum context identifier information of a first terminal device, wherein the access stratum context identifier information of the first terminal device is used to identify access stratum context information of the first terminal device that is related to the first terminal device on a first access network device; anda determining unit, configured to determining the first access network device according to the access stratum context identifier information of the first terminal device, so that a second access network device providing a network service to the first terminal device obtains the access stratum context information of the first terminal device from the first access network device, wherein the determining unit is specifically configured to:determine the first access network device according to the access stratum context identifier information of the first terminal device and a first mapping relationship, wherein the first mapping relationship is a mapping relationship between access stratum context identifier information of at least one terminal device and an identifier of at least one access network device, and the at least one terminal device comprises the first terminal device.14. The device according to claim 13, wherein a number or a bit stream that is in the access stratum context identifier information of the first terminal device and that is used to identify information about the first access network device is different from a number or a bit stream of an identifier of the first access network device.15. The device according to claim 13, wherein the first mapping relationship is a one-to-one mapping relationship between at least one piece of access stratum context identifier information and the identifier of the at least one access network device, and the at least one piece of access stratum context identifier information comprises the access stratum context identifier information of the first terminal device.16. The device according to claim 13, wherein the device is the second access network device, the first mapping relationship is preconfigured in the at least one access network device, and the at least one access network device comprises the second access network device.17. The device according to claim 13, wherein the access stratum context identifier information of the first terminal device is pre-allocated by the first access network device to the first terminal device.