Abstract: The excavation slope of the Rumei Hydropower Station in Tibet (about 700 m high) is taken as an example in this paper. Through the detailed site investigation of the unloading, a study of the distinct element modeling deformation response of the large scale excavation is carried out on high rock slopes under complex geological conditions. This distinct element modeling gives the deformation response process, the basic laws and geology mechanics model of the slope under unloading conditions. The simulation results show that after the large scale excavation of the high slope, the deformation of the high slope has a strong connection with the position, and the upper part of the excavation face tends to have large deformation. The dominant modes of slope deformation are mainly the cataclastic rock mass in the shallow surface and the geological and mechanical response of slipping tension fracture in the deep part. There is a close relationship between the slope deformation and the rock unloading after excavation. With the excavation progresses, the slope deformation increases with the excavation, the deformation of the lower part gradually decreases, and the deformation mainly accumulates on the upper part of the excavation, and finally tends to be stable.