As a large box-bearing structure, the body of the special vehicle must not only bear various loads, but also have a certain protective capacity. As an important carrier in the whole life cycle of special vehicles, the structural design and test mode analysis of body-in-white have an important impact on the performance and reliability of special vehicles. In order to obtain the dynamic characteristic parameters of the body and verify its structural rationality, the calculation mode and test mode analysis of a wheeled special vehicle body-in-white were taken as the research object. The reliability of the finite element model is verified by the comparison and analysis of the modal simulation and the experimental results.