The disclosed method and system is in use for solving issues of communications memo and network security etc. The method includes steps: backup system sends first type message of media stream of backup user to next generation network (NGN) in order to appoint user needed to carrying out backup of media flow; when being detected appointed backup user of participating in calling, soft exchange equipment in NGN directs device of possessing function for replicating media to copy media flows from each parties in call, as well as sends second type message including progress information in call setup procedure to backup system, and receives third message of media flow; after carrying out mixing and copying media flow from each parties in call the appointed backup user participates, the device of possessing function for replicating media sends the mixed and copied media flow to backup system for media stream; the backup system receives and processes user media flow.