Abstract: The unexpected strong 5.12 Wenchuan Earthquake caused great economic losses and casualties and affected a large area of Sichuan.After the Wenchuan Earthquake,there were severe secondary geological disasters on the highway from Yingxiu to Wolong.the traffic was usually snarled,which influenced the highway safety operation and reconstruction seriously.What’s more,the post-earthquake collapses are a secondary geological disaster with the wide distribution,severe shatter and large potential threat under the action of strong earthquake.This paper analyzes the formation mechanism on post-earthquake collapses in depth.It takes the highway from Yingxiu to Wolong with more post-earthquake collapses as the research object.It combines with predecessors’ achievements on Wenchuan Earthquake.It is based on the detailed survey about the post-earthquake collapses of slopes near the sides of the highway from Yingxiu to Wolong and 115 profiles.There are four stages of post-earthquake collapses from start to finish.Namely,they are the original structure,potential variable body,shattering rock and collapse.On this basis,the formation mechanism on the post-earthquake collapses of highway slopes can be described as four models including shatter-slip collapse,shatter-dump collapse,shatter-burst collapse and shatter-offset collapse.Because of the complex rock mass structure,there are usually two or three collapse formation mechanisms with a certain way together in the collapse disasters and the formation mechanisms change from one to another during the constant process of evolution and development.However,among them,there is one mechanism which first happed as the major in the collapse.These reveal that the mechanical mechanism of the slope rock mass changes, and determines the final damage forms and features of post-earthquake collapses.The paper makes expatiation of their formation mechanisms.These results provide a powerful reference for highway reconstruction and disaster prevention and mitigation.At the same time they also provide the technical support for such the problems including disaster reduction countermeasures of transportation infrastructure under the influence of the earthquake and the methods for dealing with to clear the road blocked by the collapse,highway slope collapse disasters prevention in the mountainous area and earthquake disaster prevention highway recovery.