Abstract: In the slope stability analysis,the limit equilibrium method and strength reduction method have been widely applied;Compared with limit equilibrium method,strength reduction method not only can get the safety factor of the slope,but also the soil plastic strain,stress and displacement;However,it cannot be used to calculate the reinforced soil ideality.In this paper,through the analysis of reinforced soil reinforcement mechanism,regard the reinforced soil as a whole according to the equivalent stress method,using a new cohesion to replace the original soil cohesion,so as to realize the strength reduction method.Take a high fill slope in Shanxi as an example,it adjusts the equivalent cohesion of reinforced soil using the result from safety coefficient of limit equilibrium method,then comparative analysis the equivalent cohesion in different height slope,finding out that the slope height will have influence on the increment of cohesion,the higher of slope,the greater of the increment cohesion.The results of finite element method can be used to optimize the design of slope,and to provide a way for research reinforced soil.