Due to the network prolonging or fault

inconsistency or synchronous problem of the initial state of cooperative sites occurs when they join a real-time cooperative editing system at different time.Furthermore

the fault of cooperative sites or network

or long time no operations in cooperative sites

and the fault-tolerant of session manager can affect reliability of the system.A multiple late-join server algorithm is presented.The algorithm can effectively solve the consistency of the initial state of the late-join client.A query algorithm and distributed backup model based on session manager are proposed to guarantee the reliability of cooperative editing systems.The effectiveness of relative algorithms is verified by a concrete example.