The stability and treatment of cataclinal hard-rock slope are very important to construction of highway.This paper deeply analyses the topography, lithologic and tectonic features of stratum, hydro-geologic conditions in one slope. Numerical simulation software UDEC is used to simulate the deformation and failure characteristics of the slope and get the deformation and failure mechanism of it. The result indicates that the joint of weathering and unloading of the slope are developed because of long-time weathering, and the joints are filled with silty clay, thus the shear strength reduces greatly and this leads to the sliding of the moderate-dip cataclinal slopes. The conclusion may be useful for the stability assessment and regulation measures of similar engineering. Furthermore, it proves that the discrete element method is very effective to numerical simulation on bedding rock slopes.