A communication method, apparatus, and system are disclosed, to provide a mechanism of mobility, of a terminal device that supports private networks, between the private networks. The method includes: a first access network device determines, based on a first list, a target cell that belongs to a target first network, where the first list includes an identity of at least one first network to which a terminal device subscribes. The first access network device sends a first message to a second access network device that serves the target cell, the first message carries a second list, the second list is used to enable the second access network device to determine the identity of the at least one first network to which the terminal device subscribes.