Abstract: According to the spatial morphology problem of the slope in the in pit dumping site at inclined weak-basement, taking Baiyinhua No. 3 surface mine as an engineering background, based on the means of the rigid body limit equilibrium and the 3D numerical simulation, the paper had an analysis on the in pit dumping angle and the in pit dumping site development to the different engineering location affected to the slope stability of the in pit dumping site. The results showed that the landslide mechanism of the slope in the in pit dumping site of Baiyinhua No. 3 Surface Mine was that a plastic yield was occurred in the weak layer of the basement under the self gravity role of the dumping material. And the sliding surface linkage was occurred from the inner of the dumping material and would form a shearing layer-bedding sliding with a shearing arc as the lateral interface and the base floor as a bottom interface. The slope parameters of the in pit dumping site could meet the safety requirements when the in pit pushing distance was 1 000 m, the in pit dumping angle was 14° and the bench width was 67 m. The slope of the in pit dumping site with a bedding inclined weak-basement would be reduced with the in pit dumping slope angle and would be increased with the pushing distance. The slope stability of the in pit dumping site would be increased linearly. The in pit dumping angle would have obvious influences to the slope stability. Therefore,the spatial morphology of the slope in the in pit dumping site at inclined weak-basement could be determined.