A suspension roll mechanic model was set up, and by using the initial parameter method of structural mechanics, the analytical solution of the torsional stiffness of torsion beam with stabilizer bar was deduced, on the basis of which the mathematical model of its equivalent roll stiffness at the wheels was established. The mathematical model was verified by simulating the corresponding model set up with ABAQUS software. Then, combined with NSGA-Ⅱ algorithm, an optimization was conducted on the roll stiffness and the total quality of the beam. The results have shown that the roll stiffness and total quality of the beam get a good balance and the optimization method is reliable, which has theoretical guidance for the design and choice of characteristic parameters of the torsion beam rear axle in the primary stage of development.