Abstract: Through investigating geological hazards of Beichuan Chenjiaba town in Wenchuan earthquake disaster areas, according to engineering geologic analogy method, calculating model and seismic wave are chosen reasonably based on the investigation and analysis of the loose soil slope failure , FLAC^3D simulation software and rock and soil masses of elastic-plastic theory are adopted to analyze the shear and tension failure law and shear strain dynamic response of the stratified soil element under dynamic load. The study shows that the shear failure of slope element inside the slope body will appear firstly, along with the time vibrations, shear failure elements extend to the toe and top of slope, and the tension failure mainly happens along the slope shoulder. It will cause the slope failure suddenly when shear failure surface and tension failure surface is connected. After the earthquake, the slope toe deflects to free face, meanwhile, the slope shoulder subsides, finally the failure surface of slope presents arch failure.