The dispatch and centralized control mutual backup system based on multi-domain sharing technology is proposed. The realization of supervisory control and data acquisition（SCADA） function mutual backup between dispatching automation and centralized control systems by data synchronization， data security， data exchange， multi-level inter-backup， and other key technologies， is discussed. The practical application shows that the proposed system can meet the security level and emergency processing capability requirements of dispatching automation system and centralized control system.