Suspension design is one of important technique to develop automobile. Since suspension system has strong non-linearity, it is difficult to optimize the suspension system by Gradient Based Method. Authors discussed the benefit of Genetic Algorithms to optimize the suspension system in this paper. Prototype of optimization system for suspension systems based on Genetic Algorithms was developed. In this system, the suspension system was analyzed and evaluated by Mechanical System Simulation Software ADAMS. The validity of the optimization system was clarified through the two case studies focusing on toe curve and lateral stiffness. Typical double wishbone type rear suspension with twenty design variables was analyzed and optimized by the optimization system.