In order to study the dynamic characteristics of electric vehicle body-in-white, a structural modal parameter identification method based on natural excitation is proposed. By this method, the structural modal parameters of an electric vehicle body-in-white is identified. The first three-order structural modal parameters of the electric vehicle body-in-white are obtained, then the results of identification by this method are compared with those by traditional methods. It is found that the maximum error of natural frequency is 1. 8%, the maximum error of damping ratio is 13%, the modal shape is consistent, the correctness of this method is verified. Then, the dynamic characteristics of the Body-in-white of the electric vehicle are evaluated by the identified structural modal parameters and the working characteristics of the electric vehicle. The proposed natural excitation method simplifies the identification process of structural modal parameters, and can be applied to identify modal parameters of large and heavy structures which are not easy to excite. The results of modal parameter identification have certain guiding significance for the dynamic characteristic design of electric vehicle body in white.