Embodiments of the present invention provide a method and a device for transmitting downlink data in multiple UEs cooperative communication. A base station selects a benefitted user equipment UE, where the benefitted UE and a supporting UE are UEs in a closed cooperative group, each data radio bearer of each UE in the cooperative group corresponds to a logical channel identifier LCID, and the LCID is unique in the cooperative group; the base station generates a media access control packet data unit MAC PDU, where the MAC PDU comprises data to be sent by a data radio bearer of the benefitted UE, and a LCID corresponding to the data radio bearer, and the base station sends the MAC PDU to the supporting UE. The above solutions achieve a method of multiple UEs cooperative communication for synthesizing on the MAC layer.