In the process of exploiting and trial-manufacturing the bus school, we find the small stiffness is insufficient, and there exits such phenomenon that small skin fractures and deformations. This paper Builds a three-dimensional model of the school bus by using CATIA software, and then imports the model into Workbench software, establishing a body frame finite model for free modal analysis. Analyzing the free modal of the body frame based on Workbench, we get the body frame’s inherent frequency and vibration mode, and evaluate the body frame vibration characteristics, and put forward improvement proposal on the problem of body frame.