Abstract: Debris or mud flow caused by the landside is one of complicated geologic hazards in mountain area, which is usually related to geology, lithology, the mechanical characteristics of the rock and soil, rainfall, groundwater, and land usage condition. The analysis of immanent relationships between landslide and mud flow can not only afford a reference for the analysis of landslide failure mechanism, but also be used as the basis of evaluation of mud flow triggered by landslides. In this paper, the depth integral is applied two two-dimensional mathematical model of mud flow. The model is based on the principle of conservation of mass and viscous Newtonian fluid Navier-Stovkes equation. Then, this equation is numerically computed by using the finite difference method. The relational expression between streams tilt angle and the width of affected range of mud flow is obtained from statistics. It is applied to analyzing the possibility of mud flow induced by landslides which once failed under the similar geological conditions. Combining with GIS,the model can also be used to predict impacted range of mud flow by using risk map to show the zones that may be affected by the mud flow.