Embodiments of the present invention provide a method, a base station, and a user equipment for implementing carrier aggregation. The method includes: determining, by a primary base station, to add a cell for a user equipment UE; and sending, by the primary base station, a first message to the UE, where the first message is used to instruct the UE to add the cell, the first message includes configuration information of the cell and an identifier or index of a base station to which the cell belongs, and the base station to which the cell belongs is a secondary base station. In the embodiments of the present invention, under the control of the primary base station of the UE, a cell of another base station can be added for the UE, so as to implement carrier aggregation between base stations, thereby further increasing user throughput of the UE.