Applying the 3D design and finite element technology to the design of city bus body, the model analysis of bus body frame was carried out. On the basis of general modeling of bus body, the locus of bus body frame was constructed in light of the inner surface profile of body cover panel. The 3D models of both bus body frame and floor frame were constructed under Pro/E, and the virtual assembly of them was completed. By leading the wire frame model of bus body frame in ANSYS software, its FEA wire frame model was obtained. The natural frequency and vibration mode of bus body frame can be known by means of model analysis. It lays the foundation for the FEA of whole bus body frame.