A shunting method and system for multi-network joint transmission and an access network element are provided, and the method includes that a network element of a 3GPP access network transmits a shunting request message to a network element of a WLAN access network; upon reception of a success response from the network element of the WLAN access network, the network element of the 3GPP access network transmits to a UE a shunting command to indicate the UE to access a target WLAN access network corresponding to the network element of the WLAN access network; and after determining that the UE has successfully accessed the target WLAN access network, the network element of the 3GPP access network performs data shunting transmission through a shunting connection between the network element of the 3GPP access network and the network element of the WLAN access network. By means of the disclosure, it is possible to implement shunting control over multi-network joint transmission by a network side.