Abstract: In order to obtain the scientific,resonable,quantitative and qualitative evaluation results of the accident risk of the open pit mine slope,according to the accident tree structure theroy, fault tree model of the open pit mine slope is established at the base of analyzing and summarizing instability factors of the open pit mine slope.The key factors that affect the open pit mine slope instability include that weak plane exists,the complicated regional geological structure,groundwater effection,illegal mining,management and institution construction are obtained by the calcuation of minimal cut sets, minimal path sets and the importance of structure.In line with the research results,some corresponding prevention measures are put forward.It have great important guiding significance for preventing and controlling of the open pit slope instability.

Key words: Fault tree analysis method, Slope instability, Prevention and control measures