Using the theory of upper bound limit analysis method and the volume force increment method, considering the defects of limit analysis model of a single sliding surface, an arbitrary block model considering the dislocation effects of multiple rock layers with structural joints is established. When the rock mass reaches the limit state (destruction) under external load, the work that is done by external loads is equal to the work that rock mass absorbs. Based on this premise, relevant equation can be established; thereby the calculation formula of slope stability coefficient can be derived. After analyzing typical numerical examples of slope and comparing to results of discrete element numerical simulation, the feasibility and applicability of this method are verified. A calculation of bedding rock slope located in Puli-Xuanwei highway in Yunnan province is achieved, the result shows that the stability coefficient is close to the result obtained from discrete element numerical simulation. The coefficient is slightly larger, but the slope is stable. It provides a new calculation method for evaluating the stability of this kind of slope.