Abstract: Debris flow is a kind of natural disaster which appears rather frequently in the mountain areas in China. The reason of such a fact consists of two parts: the original tectonic and the contrived damage. In the process of the Western development, the investigation and analysis of the debris-flow's potential dangerous areas and its activity degree are of great importance for the establishment of practical resource exploitation stratagem, and the protection of those plants which are in the areas of high potential danger. With the technique of remote sensing(RS) and the software of watershed (such as ArcGIS and WMS), and completely based on the image and data from RS, the paper investigates a new assessment method of debris activity degree.