A subscription update method includes receiving, by a second mobility management network element (MMNE), event subscription information of a first terminal from a first MMNE, where the event subscription information includes information about a first subscription to a first event, the information about the first subscription includes group subscription identification information, the first terminal belongs to a first user group, and the first event is an event subscribed to by a unified data management (UDM) for the first user group, allocating a second subscription correlation identifier if the second MMNE has no subscription to the first event, and sending a first message to the UDM, including the second subscription correlation identifier and the group subscription identification information.