Abstract: A new method to analyze the stability of rock slope was proposed by using block element method and plastic limit analysis.In view of the mechanical behaviors of rock mass,the rock-structural plane model was used.The block elements were assumed to be rigid,stresses only existed in structural planes,and all discrete block elements were joined by these structural planes.Based on the plastic lower limit theorem,and regarding the stresses of structural plane as unknown variables,the statically admissible stress fields satisfing the equilibrium and boundary conditions and yield criterions were constructed.By using the idea of nonlinear programming,the lower bound limit analysis model of mathematical programming for slope stability was established.The results of three examples indicate that the present method can get the slope safety factor directly without calculating potential sliding patterns one by one and the results of this method is quite close to those from the rigid limit equilibrium method.