This application provides a transmission method for retrieving old context of a terminal device, the method includes: a first network node sends a first message to a first system, where the first message is received from a terminal device and includes CRNTI allocated previously by the first network node for the terminal device; the first system sends a second message to the first network node, the second message comprises identification information of the terminal device which is in association with old context information of the terminal device that is stored at the first network node, and is used by the first network node to retrieve the old context information of the terminal device.