Based on modal experiments, the car-body finite element model is updated applying the support vector machine response surface method (SVM-RSM) model updating theory, which is used to increase the low precision of the flexible car-body finite element model in a rigid-flexible coupling dynamic simulation model. The first six frequencies and modes of the car-body are extracted using modal analysis through ANSYS software. The modal experiment program is designed, and the modal information of the car-body is tested to validate the finite element model based on the errors of both FE model data and tested data. The elastic modulus and density of the car-body are updated using the SVM-RSM model updating method. Model validation and the application of the dynamic model show that the precision of the updated finite element model has advanced so much that it can accurately reflect the structure characteristics of the car body and provide the exact model for a foundation for firing accuracy analysis.