Abstract: Southeast Tibet is an area with high frequency of debris flow, and also the place G318 pass through. Debris flow poses a serious threat to local social development and major engineering construction. In this paper, according to the conditions of southeast Tibet, 11 disaster-causing factors such as highway distance, watershed distance, fault distance, elevation, slope, rainfall and NDVI etc. are selected to study the occurrence regularity of debris flow in this area. Each factor data of debris flow point is derived and analyzed in ArcGIS, correlation test is carried out and factor sensitivity grade is established. After calculating the weights by AHP, the risk distribution map of debris flow in southeast Tibet in 2015 was made by combining factor sensitive layers to verify the correctness of the model. Different risk distribution maps are made according to different rainfall sensitivities to predict the future debris flow prone areas. When the rainfall sensitivity of the whole region is 3, nearly half of the southeast Tibet is highly prone to debris flow, and all along G318 are in high risk areas. When the rainfall sensitivity is 2, there is no extremely high risk area in southeast Tibet, the risk index of the whole region is greatly reduced, and the high risk part along G318 accounts for 84.56%. The results show that rainfall has a great influence on the risk distribution of debris flow in the study area. The research results can provide theoretical support for the social development and major project construction in southeast Tibet.