According to the survey results of Dacun and Jiancun villages of Shijiaying Town, Fangshan District,  Beijing City,  the authors established the 3D engineering geomechanics model and elasticity-plasticity model on the slope stability near the residential areas. By the finite difference method, the authors analyze and contrast the safety coefficients of the two kinds of slopes （single waste rock pile slope, waste  rock mass mixed slope） between the natural and saturated states. Finally, the slope risk was evaluated.