Abstract: Open-pit mine step height increase has positive significance for the enterprise, but the material of the dump is heterogeneous and discrete, and the mechanical properties of the lower materials are different with the increase of the height, so, it is necessary to refine the evaluation of the safety and stability of the slope while improving the height of the soil dumping step, and to optimize the height of the step from the perspective of safety. In this paper, the mechanical properties of the material under different consolidation pressures are obtained through laboratory test and numerical simulation of the material obtained from the dumping site of the open-pit mine in Tianchi Energy South Open-pit Mine, Xinjiang. By means of DEM numerical simulation, the change rule of the safety and stability coefficient of the dump steps in different areas and at different heights was obtained. The results show that with the increase of consolidation pressure, the degree of internal cementation and the mechanical strength of the sample increase. The instability of the inner dump slope will lead to circular arc landslide, which is characterized by uneven settlement at the top of the slope in the initial stage, and a large amount of slope particles rolling down in the later stage. When the strength reduction exceeds the safety stability factor, the velocity of the particles on the slope will change abruptly. The safety and stability coefficient and the step height change as a logarithmic function. The stability of the bottom dump step is better than that of the common dump step, and the bottom dump step cannot maintain stability when the height is 75 m.