Discrete element method is a numerical methods using for non-continuous media, which is suitable for high rock slope stability analysis with developed rock fault, joints and cracks. Strength reduction is a numerical methods, widely using in the slope stability analysis, it maintained that the strength reserve coefficient and the stable safety factor proposed by the limit equilibrium is equivalent. Combining the discrete element method with the strength reduction criteria, using two sets of grids: Dense grid represents the condition of joints; Dilute grid is approximate equivalent to the conditions that the rock's integrity is improved after reinforcement. It calculated the high slope of Goupitan plunge pool, analyzed the stability of the natural slope and excavated slope and evaluated supporting effect, this provided a reference for the design and construction of the project.