Abstract: The method of FMMD(Failover Mechanisms for Multi-domain Distributed SDN Controllers) Failover is proposed in this paper to solve the problem of fault removal for multi-domain distributed SDN controller. The two problems that independent switch rejoin in the network resulting from a failure of the controller are mainly solved.First, how to quickly rejoin the independent switch to the network (how to quickly restore the communication of whole network); Second, how to prevent the overload of controller due to the addition of new switches. Experiment shows that the method of FMMD Failover can effectively reduce the time of fault transfer and the average delay time of the end to end, and the scalability and flexibility of the SDN network are effectively improved.