Abstract: This paper focuses on 6 debris flow gullies in the small watershed. Based on field investigation and remote sensing image interpretation, the numerical simulation of debris flow process in the actual rainfall frenquency was made by FLO2D. It shows the deviation ratio in fan area is between -25%-12%, in runout amount is between -16%--1%, which shows the simulation results are bettercompared with the actual situation.Meanwhile, we carried out the debris flow hazard analysis and the outcome shows the area proportion of high hazard,medium hazard and low hazard accumulation zone of the total area. In addition, according to the debris flow simulated results of 5% and 1% rainfall frequency under the same parameters, average deposition depth ofalluvial fan , alluvial fan area and the runout amount under three different frequencies, it can provide reference for debris flow hazard assessment, disaster forecasting, engineering treatment and hazard zone partition in study area.