Abstract: With the development of the highway in mountainous areas, the problem of slope engineering rock mass is increasingly manifold in many different ways. For the sake of recognizing the characters of excavation engineering rock mass in nature, the authors, who, based on the unloading rock mass mechanics, discuss the deformation and destruction characters, the methods of stability analysis and the design theories of the slope engineering rock mass. The research results indicate that the characters of deformation and destruction of the slope are not the same as those of the regular loading rock activities, but conforms with those of unloading rock mass mechanical activities. While the stability analysis of slope rock mass emphasizes hydraulics and unloading effect, and some essential expressions are obtained. It is assumed that the excavation design of the slope engineering rock mass will acquire cost efficiency and optimization only if it is worked out based on sufficient recognition of the engineering mechanics with the consideration of the geological characters and all kinds of data available for the stable slopes.