This paper presents the study of chassis tuning of a commercial vehicle, which has a rear suspension with dual stage leaf spring assembly and a front suspension with double wishbone torsion bar. To balance the handling and ride performance of the vehicle, it is necessary to tune the key suspension parameters of the chassis including the dual stage stiffness of the leaf spring, the contact load of the leaf spring, the torsional rigidity of the torsion bar, the force curve of the front and rear dampers etc. The chassis tuning process of a physical commercial vehicle was first put forward. In the proposed flowchart, the kinematics and statics of front & rear suspensions were checked at the beginning of the tuning. Then the tire mechanical characteristics were tested by using a plate-type tire tester and the inertial parameters of the vehicle were indirectly measured. The K&C characteristics of front and rear suspensions were also tested and compared with the benchmark vehicle's. Next the virtual model of the commercial vehicle was established and verified based on the handling and ride test of the vehicle, and then the virtual model's handling and ride performance were respectively analyzed by simulation. After that, a classic genetic algorithm was used to conduct virtual optimization of the suspension parameters and the optimised parameters were obtained. According to the optimized results, several sets of suspension samples were manufactured, and then they were respectively installed to the commercial vehicle by a DOE test method. At last, the subjective and objective evaluation trials of the vehicle were performed respectively in different groups. The results show that handling and stability of the tuned commercial vehicle has been improved while reducing the development cost and cycle.