A data forwarding method for interworking between a first network and a second network, the first network and the second network are two different networks, the method comprising: sending, by an access and mobility management function network element in the second network, information about a first bearer in the first network; receiving, by a session management function network element from the access and mobility management function network element, the information about the first bearer in the first network, wherein the session management function network element integrates a packet data network gateway-control plane in the first network and a session management function in the second network; determining, by the session management function network element, a first flow in the second network based on the information about the first bearer and association information, wherein the first flow is a flow for data forwarding, wherein the association information indicates an association between the first flow and the first bearer; and sending (203, 204), by the session management function network element to an access network device in the second network via the access and mobility management function network element, flow information of the first flow and forwarding information, wherein the flow information indicates the first flow, and the forwarding information identifies a user plane function network element to which to forward the first flow, wherein the user plane function network element integrates a user plane function in the second network and a packet data network gateway-user plane in the first network for forwarding the first flow to a tunnel corresponding to the first bearer. sending, by an access and mobility management function network element in the second network, information about a first bearer in the first network; receiving, by a session management function network element from the access and mobility management function network element, the information about the first bearer in the first network, wherein the session management function network element integrates a packet data network gateway-control plane in the first network and a session management function in the second network; determining, by the session management function network element, a first flow in the second network based on the information about the first bearer and association information, wherein the first flow is a flow for data forwarding, wherein the association information indicates an association between the first flow and the first bearer; and sending (203, 204), by the session management function network element to an access network device in the second network via the access and mobility management function network element, flow information of the first flow and forwarding information, wherein the flow information indicates the first flow, and the forwarding information identifies a user plane function network element to which to forward the first flow, wherein the user plane function network element integrates a user plane function in the second network and a packet data network gateway-user plane in the first network for forwarding the first flow to a tunnel corresponding to the first bearer.