Abstract: Slope stability has great effect on safety and high efficiency mining for opencast coal mine. On the basis of systematically summarizing occurrence condition of opencast coal mine in eastern Inner Mongolia, this paper proposes key factors for slope engineering geological characteristics and stability. Using the orthogonal test and range analysis method, we conducted research on the factor sensitivity affecting slope stability of open pit coal mine. The results show that four key factors which control the open pit slope stability in this region are distribution of weak structural plane, strength and deformation of weak structural plane, groundwater drainage effect and comprehensive slope angle. The sensibility of the influencing factors of slope stability changes during different mining phase, the slope stability control strategy and emphasis also should be adjusted accordingly, this has certain guiding significance for slope control of opencast coal mine in eastern Inner Mongolia.