Aiming at the characteristics of the conceptual design of bus body structure, a bus body structure conceptual design and optimization system was developed, and a parameterized bus body structure conceptual model was constructed. With the model of the conceptual model as the template, the new bus body structure conceptual geometric model can be created and body size parameters can also be adjusted. This system can implement static stiffness analysis, low modes analysis, sensitivity calculation and optimization design for the body with automation process. Therefore, the body structure performance and lower order mode performance can be evaluated effectively. Finally, the paper showed a case of analysis. The case calculated the body structure stiffness and the low modes of a bus, and improved the stiffness and low modes by ensuring the quality of the body invariable, which improved the body structure performance, and realized the body lightweight. The case has verified the reliability and effect of the system.