a method of network resource release processing is provided , which includes the following steps . after user equipment using idle mode signaling reduction mechanism registers to two 3rd generation partnership project communication networks , when the ue changes from the 3gpp network to a non - 3gpp communication network , a serving gateway receives a message sent from a peer endpoint network element , and deletes network resources established by the two 3gpp communication networks for the ue according to the message . a mobility management ne and a serving gw are also provided . through the method and device of network resource release processing , the resources are released when the ue using the isr mechanism changes from the 3gpp network to the non - 3gpp communication network .