Abstract: In this paper the influence of atmospheric precipitation on moisture content and volume weight landslide body and hence the influence moisture content in soil on internal friction angle and cohesive force are discussed. Based on these influences, two different initiation mechanisms for landslide are presented. The models for forecasting initial velocity, pushing force, direction, and time of initiation are established based on these relationships involving factors of precipitation moisture content volume weight and internal friction angle cohesive force stability. At the same time, numerical simulation of landslide initiation mechanisms is accomplished by GIS.