A method for detachment of a mobile set within the equivalent route area moving between the communication systems comprising steps of: during the detachment process is implemented between a mobile set and a service node in one communication system, the service node generates one or more messages and transmits it to the service nodes in one or more communication system within the ERA. If the message is transmitted to the service node within the ERA of only one communication system, this service node transmits this message or the message generated according to this message to the service nodes within the ERA of the other communication system. With the method proposed in present invention, when a mobile is detached from two or more communication systems which share the same ERA, the service nodes in all communication systems within the ERA can still correctly manage the relevant information on this mobile set.