Abstract: The Jiaobangou Basin in Dechang county have some features such as large watershed area, complex and diverse topography, rich rainfall and abundant sources which provide the potential conditions for causing debris flow. This paper analyzes the pregnant environment characteristics and the formation conditions of debris flow, and divides the multi-scale assessment units of debris flow watershed based on topography and geological conditions. On the basis of analysis, the debris flow hazards are quantitative assessed by the multi-factor coupling method of topography, geology and hydrology. Using the method of hydrological analysis, Jiaobangou watershed, the watershed area of 45.71km2,which divided into 28 assessment units(8 units in the early mature stage, 13 units in the full mature stage, 5 units in the late mature stage and 2 units in the old stage), is accurately calculated 8 high hazard areas, 6 medium hazard areas, 10 low hazard areas and 4 safe areas. The hazard assessment is close to actual experiences in Jiaobangou watershed, which can provide great significance to the disaster prevention and mitigation in the area.