Abstract: The slope stability of Heishan Open-pit Mine is analyzed, and the stability and failure mechanism of internal slope are studied by ANSYS software on the basis of theoretical analysis of internal slope stability. The results show that the landslide model of the dump slope in Heishan Open-pit Mine is “sitting slip” sliding, and the stability coefficients of section NP1-1 and NP1-2 are 1.003 and 1.015, respectively, which are in the limit equilibrium state, far less than the requirement of safety reserve coefficient 1.2. In order to ensure the stability of the slope of the inner dump and prevent the occurrence of landslide accidents, it is necessary to carry out slope cutting treatment of the internal dump, and strengthen the inspection to ensure the safety of production in the open pit mine.