A communication method, wherein the method comprises: receiving, by a first device, a first message sent from a second device, wherein the first device is a primary access network device of a terminal device in a first state, the terminal device in the first state does not send channel state information to the first device, and a core network device and the first device reserve a data plane connection of the terminal device in the first state; determining, by the first device based on the first message, that the second device is a secondary access network device of the terminal device in the first state; sending, by the first device, a second message to the second device, wherein the second message is used to request to add the second device as the secondary access network device of the terminal device in the first state; and receiving, by the first device, an acknowledgment message that is for the second message and that is sent by the second device based on the second message; wherein the receiving, by a first device, a first message further comprises: receiving, by the first device, a cell update message of the terminal device in the first state, wherein the cell update message is used to indicate that the terminal device in the first state moves from a cell covered by the first device to a cell covered by the second device; and the determining, by the first device based on the first message, that a second device is a secondary access network device of the terminal device in the first state comprises: determining, by the first device based on the cell update message, that the second device is the secondary access network device of the terminal device in the first state. receiving, by a first device, a first message sent from a second device, wherein the first device is a primary access network device of a terminal device in a first state, the terminal device in the first state does not send channel state information to the first device, and a core network device and the first device reserve a data plane connection of the terminal device in the first state; determining, by the first device based on the first message, that the second device is a secondary access network device of the terminal device in the first state; sending, by the first device, a second message to the second device, wherein the second message is used to request to add the second device as the secondary access network device of the terminal device in the first state; and receiving, by the first device, an acknowledgment message that is for the second message and that is sent by the second device based on the second message; wherein the receiving, by a first device, a first message further comprises: receiving, by the first device, a cell update message of the terminal device in the first state, wherein the cell update message is used to indicate that the terminal device in the first state moves from a cell covered by the first device to a cell covered by the second device; and the determining, by the first device based on the first message, that a second device is a secondary access network device of the terminal device in the first state comprises: determining, by the first device based on the cell update message, that the second device is the secondary access network device of the terminal device in the first state.