Obtaining, by a source cell, a key retention policy of a terminal device, where the source cell and the terminal device use a first key to communicate with each other; determining, by the source cell according to the key retention policy of the terminal device and a key retention policy of the source cell, whether the terminal device and a target cell use the first key to communicate with each other; and sending, by the source cell, a handover request message to the target cell, where the handover request message is used to request to hand over the terminal device from the source cell to the target cell, the handover request message includes first indication information, and the first indication information is used to indicate whether the terminal device and the target cell use the first key to communicate with each other.