he erosion and deposion of debris flow are the result of the destruction of structural stress and the gravitaive stress and strain in the nature. From the analysis of the macrosmic regional structural stress field. Jiangjia Gully is the centralized region of the main compressive stress of Xiaojiang fault, and located in the second rotatory structure. The tension crack, propulsion, avalanche and wriggle-slide caused by the concentrative stress on slope, provid the source of the loose solid materials. In Jiangjia Gully, the sloping land with  more than 25 degrees accounts for 51 percent in the total land. The limiting balance of the stress on slope is controlled by the slope degree and the optimum moisture content. The depositional landform is influenced by the stress attenuation of the fluid.