A new approach for calculating tension strength of reinforcement in reinforced earth slopes is presented. Based on the theory of anisotropic apparent cohesion, the essential ideal of the approach is to convert the effective of reinforcement into the additional cohesion of the reinforced soil. From the internal stability analysis of reinforced earth slope, the value of cohesion need to be added to strengthen the slope is estimated and then the tension strength of reinforcement is determined accordingly. By using computer program analysis (‘PCSTABL6'') the obtained results are conveniently presented in the form of design charts. Both of tension strength of reinforcement in designing reinforced earth slope or factor of safety of the real design of slope can be determined utilizing these charts. These charts are applicable to granular backfills, the existence of porewater pressure and the slope angle of lower than 75 degree. The results are also compared to other researcher''s results and discover the favorable range of using the new method.