Abstract: A high altitude collapse on the No.108 National Highway in west Sichuan Province took place in May 25,2007,which leaded to heavy casualties and loss.By comprehensively using many kinds of means,such as geological survey,3D laser scanning technology,analysis of blasting vibration effects and statistical analysis on many historical collapse and rainfall,the paper objectively sets forth the reasons to the collapse,including high steep terrain,fractured rock mass and rainfall trigging,and so on.At the same time,blasting vibration is a minor and indirect factor to the collapse.Based on the shape of the slope and height of the collapse,through kinematics theory and energy method,the authors calculate velocity of the falling rock and impulsive force that the falling rock impacted the bus.