A service subscription method for reporting service change in a communications system is provided. In the method, a first network function network element sends a first message to a second network function network element to subscribe a first service on behalf of a third network function network element. The first service is provided by the second network function network element and the first message includes a first address of the first network function network element. When the second network function network element is changed to a fourth network function network element, the fourth network function network element sends a third message to the first network function network element according to the first address to notify the first network function network element that a subscription of the first service has changed.