Abstract: Min County is an area with frequent debris flow in the south part of Gansu Province. In order to study the movement and accumulation characteristics of debris flow, the Malu River basin in Min County, Gansu Province, which was affected by serious debris flow on May 10, 2012, is selected as the research area. Six debris flow gullies in the basin are taken as the research object, which are taken as a whole. Considering the main river's scouring and carrying of debris flow deposits, FLO-2D is used to simulate the flow situation and different rainfall frequency of the main river before rainfall. According to the field investigation results, the debris flow simulation results under the condition of 2% rainfall frequency are compared to verify the accuracy of the model. Based on the simulation results, ArcGIS is used to carry out the risk assessment, identify the high-risk debris flow gully in the basin, delimit the high-risk residential area, and make statistics of the impacted area, so as to provide scientific basis for debris flow prevention and early warning.