Abstract: In order to scientifically evaluate the slope stability of down dip soft rock with weak layer in open pit mine, a case study of an open pit inner dump slope is carried out, which is based on limit equilibrium method, monitoring data, back analysis of landslide and drilling. The results show that the landslide trend of inner dump slope is basically formed which is still in the stage of uniform deformation. A weak layer that thickness is about 2 m to 3 m occured under the coal seam floor was found to be the dominant factor of this deformation. In order to prevent the occurrence of large area landslide, cutting slope and uploading method was chosen after scheme comparison. After the control method is adopted and put into effect, the deformation is controlled, and the safe production of the open pit mine is guaranteed.