Abstract: Landslide hazards triggered by"5.12"WenChuan earthquake have special dynamic process and failure mechanisms,along the fault zone developed many rock block ejection and landslides.This paper is based on the Dazhuping collapse through Beichuan-Yingxiu fault in Gaochuan,by the investigation on the scene,majorly studied the formation mechanism and motion process of a whole ridge and high-speed rock block ejection triggered by Wenchuan earthquake,and according to the actual ejection distance,calculating the topographic amplification horizontal and vertical earthquake acceleration.The results show that under strong earthquake,the structural plane of rock mass cut by cranny by upper throwing force of P-wave and horizontal shear force of S-wave,the surface wave with huge horizontal and vertical acceleration arrives last and is enlarged by terrain,the powerful earthquake force throw the whole rocks to the inclined top,forming collapse,causing a disaster.