A method of radio bearer establishment in dual connectivity, for a first base station in a wireless communication system is disclosed. The method comprises determining whether to establish or release at least a radio bearer for the communication device on at least a second base station, transmitting a request message including information of the at least a radio bearer to be established or released on the at least a second base station, to the at least a second base station, and receiving a response message including information about accepting or rejecting establishment or release for the at least a radio bearer on the at least a second base station, from the at least a second base station.