A handover method, a device, and a system to ensure that after an access and mobility management function (AMF) entity determines to no longer serve some terminals, a current ongoing procedure of a terminal in these terminals is not interrupted. The method includes: receiving, by a target mobility management entity, a message related to a target terminal; and sending, by the target mobility management entity, the message related to the target terminal to a source mobility management entity that currently serves the target terminal.