Abstract: According to the physical and mechanical properties of rock and soil, the stability of the designed slope of the dump is analyzed respectively under three conditions: sliding along the interior of the dump, sliding along the basement and sliding along the weak layer inside the basement. In the unstable situation, the method of reserving safe coal wall was adopted to reinforce the internal dump. The improvement effect of different coal wall widths on the slope stability of the internal dump was compared, and the plan of reserving 25 m coal wall was finally determined. Finally, some suggestions and opinions are given for the matters needing attention in the process of soil drainage.