A method, device, and system that enable device-to-device (D2D) data transmissions in a cellular network. The major content comprises: a resources allocation method, specifically: a base station receives a data transmission request from a first user equipment (UE); a D2D connection has already been established between the first UE and a second UE; allocating wireless resources for data transmissions between the first UE and the second UE according to the received data transmission request, and transmitting the wireless resources allocation result to the first UE and/or the second UE; a data transmission method, specifically: the first UE transmits a data transmission request to the base station; the first UE and the second UE receive the wireless resources allocation result from the base station; the first UE uses the wireless resources allocated by the base station to transmit data to the second UE, and the second UE uses the wireless resources allocated by the base station to receive the data transmitted by the first UE. The present method enables D2D data transmissions in a cellular network.