Abstract: Based on field investigation results of high rock slope,rock mass structure characteristics and the main geological factors affecting stability of rock slope are analyzed.According to deformation and failure characteristics of natural rock slope,qualitative analysis prediction for macroscopic deformation characteristics and the failure model occurring during excavating rock slope are done.By the FLAC^3D software based on the finite difference principle and the geological model of left abut ment slope,a numerical model of left abutment slope is established and stepping process of excavating is carried out by the FLAC^3D software as a numerical method.This research obtained the changing law of stress and strain and deformation and failure characteristics of rock mass during various excavating stages of engineering slopes.The achievements from this research had guided stepping excavation of left abutment of Miaojiaba hydropower station successfully.