Coupled Torsion Beam Axle is widely applied for rear suspension because this is lighter and more advantageous in the underbody package. Recent vehicle need the additional weightdown of vehicle parts because of the regulation of the exhaust gas and the high oil price. But then it does not mean the downward perpormance. This Study present the optimized torsion beam shape, torsion beam profile and inner reinforced panel shape in keeping the roll stiffness, durability as same with the present small passenger car CTBA using design of experiment. In the study, the roll stiffness and the durability of the torsion beam alxe is predicted by Finite Element Analysis.