Abstract: Toppling failure of dangerous rock mass is a common geological disaster. In open-pit mining engineering, frequent blasting operation will cause strong dynamic disturbance to dangerous rock mass, so it is very important to analyze the failure mechanism of dangerous rock mass under the dynamic disturbance. Taking the dangerous rock mass of an open-pit mine as the research object, the failure mechanism and failure process of this type of rock mass under earthquake are studied from the microscopic point of view by using the FLAC-PFC coupling numerical simulation method. The continuous-discrete coupling method solves the shortcomings of finite difference method and particle discrete element method in simulating the failure process of slope under dynamic. The research results show that when the dangerous rock mass is subjected to earthquake, tensile cracks begin to occur on the structural plane, and gradually penetrate downward until the vulnerable rock mass is relatively weak, and toppling failure occurs with the weak point as the turning point. The toppling failure process of dangerous rock mass under earthquake can be divided into four stages: relatively stable stage, fracture penetration stage, toppling-sliding stage and collision-crushing stage.