The present disclosure provide a data transmission method, including: receiving, by a central processing node, downlink user data from a first gateway GW; sending, by the central processing node, the downlink user data to a corresponding base station; and when it is determined that an interface between the central processing node and the first GW is congested, sending, by the central processing node, a first bearer switching request message to the first GW, where the first bearer switching request message is used to instruct the first GW to bypass the central processing node when transmitting data. In the embodiments of the present invention, when determining that an interface between a central processing node and a first GW is congested, the central processing node sends a first bearer switching request message to the first GW, so that the first GW transmits downlink user data with the central processing node bypassed.