Method and apparatus for performing a voice service handover to a circuit switched domain voice service

A method includes: receiving session management information from a session management network element in a first network, where the session management information is used to request to establish a user plane tunnel of a voice service of a terminal device in the first network; and sending a handover request to a mobility management network element in the first network based on the session management information to indicate a handover of the terminal device from the first network to a second network that supports a circuit switched domain voice service. When the access network device in the first network receives the session management information to request to establish the user plane tunnel, the handover request is sent to the mobility management network element in the first network based on the session management information to establish a circuit switched domain voice service of the terminal device in the second network.