An embodiment of the present invention provides a data transmission method, which includes: receiving offloading control signaling sent by a user equipment, where the offloading control signaling carries a cellular network identifier and a wireless local area network WLAN identifier of the user equipment; establishing correspondence between the WLAN identifier of the user equipment and all bearer channels of the user equipment; determining a bearer channel corresponding to all or a part of the user data streams. Embodiments of the present invention further provide a corresponding device and system. Through the technical solutions of the embodiments of the present invention, a transmission rate of a system can be increased.