The finite element method (FEM) model was established in allusion to the semi-bearing coach car-body frame with shell elements and beam elements. And the intensity performance and dynamic performance (modal performance) were investigated. A comparison between the analytical results and experimental results of the real car-body frame was carried out, and it proved that the FEM model has a good analytical precision. The improved design of lightweight for the original car-body frame was taken according to the analytical results. The further analysis results showed that lightweight scheme is available and effectual.