Abstract: The collapse situation of entrance slope of expansion project of Huanglongtan Power Plant is introduced. The maintenance of the stability of the slope to the need for governance is pointed out. According to the characteristics of unloading rock mass and the related documents, the relation graph between the unloading quantity and the deformation modulus of slope rock mass is displayed. According to the characteristics of the entrance slope, by using the mechanics theory of unloading rock mass and the finite element method, four kinds of conditions for slope analysis are adopted, that is, the initial stress field, excavation, unloading excavation and reinforcement. The values of the maximum horizontal and vertical displacement calculated by use of the unloading rock mass mechanics theory are larger than those by the conventional methods. The variation is substantially the same for each profile. The constraint of the reinforcement measures to the horizontal displacement of excavation face of slope is not obvious, but the stress state of the surrounding area of the excavation face is greatly improved and the stability of the slope is strengthened. The results may provide a reference for the design of slope reinforcement.