A network slice selection policy updating method includes sending, by a terminal device, configured network selection assistance information on the terminal device to an access and mobility management function (AMF), where the configured network selection assistance information includes a first slice identifier. The method further includes receiving, by the terminal device, allowed network selection assistance information and indication information that are returned by the AMF, where the allowed network selection assistance information includes a second slice identifier, and the indication information indicates that the second slice identifier corresponds to the first slice identifier.