A session establishment method includes receiving, by a control device, first request information, where the first request information is used to indicate that a first terminal device requests to access a group communication service, determining a first terminal device group to which the first terminal device belongs, determining a target forwarding device that serves the first terminal device group, where the target forwarding device is a forwarding device capable of supporting a group communication service, and controlling the first terminal device to establish a session with the target forwarding device, to enable terminal devices in a same group to establish sessions with a same forwarding device such that group service access between the terminal devices in the group can be completed by using the same forwarding device.