Abstract:A dynamic finite element model for system of wheel—rail—ballast is proposed in the paper. In this computational model, the rails are discretized into plane beam elements in which the ballast is considered as additional degree of freedom. This treatment makes it pos?sible for us to assemble the stiffness,damp and mass of the ballast on the element level, which greatly reduces the band width of the total stiffness matrix. As an application exam?ple t the dynamic responses of rail track structure with different ballast thickness are analyzed and some preliminary conclusions are obtained.