A method for processing a non-access stratum message performed by a user equipment, UE, the UE comprising a configuration module (21; 51), at least one non-access stratum module (22; 52; 53), and at least two access stratum modules (23; 24; 25; 54; 55), and the at least two access stratum modules separately support different network standards, the method comprising: • receiving by one of the access stratum modules (23; 24; 25; 54; 55), from a network side device, configuration information; and • mapping the at least one non-access stratum module (22; 52; 53) to at least two of the access stratum modules (23; 24; 25; 54; 55) according to the configuration information, further comprising in a first alternative: • comparing priorities of the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed, wherein the priority is represented by quality of transmission between a corresponding access stratum module among the at least two access stratum modules to which mapping is performed and the network side device; and • selecting an access stratum module among the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed and that has a highest priority to receive a first non-access stratum message from the network side device, • receiving, by the selected access stratum module, the first non-access stratum message from the network side device; and • sending, by the selected access stratum module, the first non-access stratum message to the at least one non-access stratum module (22; 52; 53) to process the first non-access stratum message, further comprising in a second alternative instead of the first alternative: • comparing priorities of the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed; • selecting an access stratum module among the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed and that has the highest priority to send a second non-access stratum message to the network side device, and generating, by the at least one non-access stratum module (22; 52; 53), the second non-access stratum message; • sending, by the at least one non-access stratum module (22; 52; 53), the second non-access stratum message to the selected access stratum module; and • sending, by the selected access stratum module, the second non-access stratum message to the network side device. • receiving by one of the access stratum modules (23; 24; 25; 54; 55), from a network side device, configuration information; and • mapping the at least one non-access stratum module (22; 52; 53) to at least two of the access stratum modules (23; 24; 25; 54; 55) according to the configuration information, • comparing priorities of the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed, wherein the priority is represented by quality of transmission between a corresponding access stratum module among the at least two access stratum modules to which mapping is performed and the network side device; and • selecting an access stratum module among the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed and that has a highest priority to receive a first non-access stratum message from the network side device, • receiving, by the selected access stratum module, the first non-access stratum message from the network side device; and • sending, by the selected access stratum module, the first non-access stratum message to the at least one non-access stratum module (22; 52; 53) to process the first non-access stratum message, • comparing priorities of the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed; • selecting an access stratum module among the at least two access stratum modules (23; 24; 25; 54; 55) to which mapping is performed and that has the highest priority to send a second non-access stratum message to the network side device, and generating, by the at least one non-access stratum module (22; 52; 53), the second non-access stratum message; • sending, by the at least one non-access stratum module (22; 52; 53), the second non-access stratum message to the selected access stratum module; and • sending, by the selected access stratum module, the second non-access stratum message to the network side device.