Abstract: Ensuring the stability of open pit slope is the front topic of its safety in production, and the stability analysis of working slope is the basis of effective control of slope stability. Combined with the geological conditions and present situation of the slope in Weijiamao opencast coal mine, through numerical simulation calculation and analysis, the failure mechanism and failure mode of the slope are analyzed from the most intuitive displacement characteristics of slope deformation, shear strain and plastic zone expansion. The conclusion shows that the slope slips along the bottom of the weak layer with circular arc along the bottom, and causes the failure of overlying silt and silt layer. The slope body is mainly excavated and unloaded and shear failure mechanism, macroscopical. The mode is shown as the creep and crack type traction landslide, which is the failure mode of the flat push which is cut by the arc of the rear edge of the bottom plate and the trailing edge of the bottom plate. According to this conclusion and in combination with the on-site fact, the comprehensive landslide control scheme of the "Real-time monitoring + dredging and drainage + stripping" is put forward to the slope stability control, the stability of the slope is improved, and the safe and stable production of the mine is guaranteed.