Disclosed is a data transmission method. The method includes that: when downlink data is transmitted, a master node shunts, on a Radio Link Control (RLC) sublayer, the downlink data to obtain shunted data packets, and sends the shunted data packets to shunting nodes; the shunting nodes process the shunted data packets, and send the processed data packets to a User Equipment (UE); and when uplink data is transmitted, the master node converges data packets sent from the shunting nodes and data packets sent from the UE, and sends the converged data packets to a core network. Also disclosed is a data transmission system. With embodiments of the disclosure, mobile communications system is able to provide an optimized service, a higher bandwidth and better performance.