Abstract: Taking a open-pit coal mine slope instability of Inner Mongolia region as a research object and the real-time monitoring and early warning of slope deformation as the safety guarantee measure, this paper demarcates three mining stages, selects different safety reserve coefficients in stages, determines the mining process and stop-mining location in each stage, and then determines the spatial node to restore the normal mining process. The research idea and calculation method can provide reference for solving the approximate problem of open-pit coal mine.