Abstract: The flash flood disasters are one of the main hidden dangers that threatens human life and property safety and affects the social and economic development in Inner Mongolia Autonomous Region. In the new era, the prevention and control of flash flood disaster has to meet higher requirements. Based on the systematic analysis of the effectivenessand main problems of flash flood disaster defense construction in Inner Mongolia, it is proposed in this paper to build a prevention and control system of flash flood disaster and an operation and maintenance system of "online + offline" flash flood non-engineering measures based on digital twin small watershed, and standardized suggestions were put forward in terms of early warning information release, hazardous area management, project construction management and grassroots capacity improvement. This paper could provide reference for flash flood disaster prevention and control in Inner Mongolia.