This application discloses a network handover method and a network device. The method includes: receiving, by a first access network device, first session management information from a session management network element, where the first session management information is for requesting to set up a user plane tunnel for a voice service of a terminal device; and sending, by the first access network device, a handover request to a first mobility management network element based on the first session management information and a first condition, where the handover request is for handing over the terminal device from a first network to a second network, and the first condition includes that the voice service cannot be performed in the first network. This application is applicable to the field of communication technologies.