A method, a system and an apparatus can be used for transmitting data in a CA manner. A first base station currently serving a user equipment (UE), creates EPS bearers under different component carriers CC Groups for the UE. The UE sets different access stratum entities corresponding to the CC Groups to process data in the process of creating the EPS bearers. The UE determines, when transmitting or receiving data, a corresponding CC Group according to an EPS bearer that bears the data. An access stratum entity corresponding to the CC Group processes the data that needs to be transmitted or received, a site is a first base station currently serving the UE or a second base station currently serving the UE.