Abstract: Based on 109 tunnel landslides of Baoji-Chengdu Railway, the earthquake jointed rock slope instability mechanism is studied by using discrete element numerical simulation to simulate the dynamic response and the development process of plastic zone under earthquake action. The safety factor of the slope is calculated under earthquake action by using the strength reduction method. The results show that tensile failure occurs in the slope surface, and it extends from the lower part to the upper part along the slope in the beginning. Under the earthquake, the zone of tensile failure is gradually developed to the internal part of the slope, and the lower part of the tensile failure gradually expands and extends from the lower part to the upper part. There is a strong crack on the slope surface, and the rock slope will slump while the zone of tensile failure is formed.