Signaling reduction method, device and system

The embodiment of the invention relates to a signaling reduction method. A second signaling reduction network device of a second routing area receives a routing area update request sent by the UE; if the second signaling reduction network device and a first signaling reduction network device of a first routing area prior to routing area update initiated by the UE do not activate idle-mode signaling reduction ISR for the UE, the second signaling reduction network device negotiates with the first signaling reduction network device to activate ISR for the UE, and after the activation of ISR for the UE is confirmed, a network register device is notified; and the network system supported by the second routing area is different from the network system supported by the first routing area. The embodiment of the invention also provides a signaling reduction device and a system. The embodiment of the invention effectively improves the problem of signaling load caused by invalid RAU between different network systems wit