According to the auto-motor industry development, the requirements of vehicle performance and safety are getting higher. On the other hand, the car was required lower oil rate because of the environment protection and energy saving requirement. So how to get a safety car throught a simple construction which resulting of a lighter vehicle body should be considered in vehicle design. The study based on the production practice was focused on the improvement of the skin panel strength, the assembly structure design and welding process. The skin panel strength was studied by CAE including the study on skin panel sculpt, material, stamping process , and through the experiments on the assembly construction and welding process，the case about improving door assembly strength was confirmed.