According to a case of once again high soil slope instability in Nianzigou coal mine and combined with the field survey data, the analysis is carried out on the causes of landsliding instability. The numerical calculation is made by using ABAQUS finite element analysis software and the shear strength reduction coefficient method, the parameters of the safety factor and the sliding surface of the soil under the saturated state are obtained, and the potential damage process of the landslide is analyzed. Based on the relevant provisions of specifications, the landslide sliding force is calculated by using the concept of polyline sliding surface and implicit solution of transfer coefficient method to provide the basis for optimization. By optimizing the design of support structures, the adverse impact of rainfall on the slope is reduced and the slope deformation can be controlled.