Abstract: In order to analyze the influences of cracking of CRTS (China railway track system) Ⅱ slab track on subgrade on a vehicle and ballastless track, a finite element model for beam body on an elastic foundation and a vertical coupling dynamical model for a vehicle-track-subgrade system were established on the basis of the elastic foundation beam theory, the finite element method and the wheel-rail coupling dynamics theory. ANSYS/LS-DYNA, a large finite element software, was used to analyze the static and dynamic properties of track and the stability of a train under track slab cracking. The analysis results show that track slab cracking has less effect on the stress of track and has no effect on the stability and security of a train. With increase of train speed and cracking of track slab, the wheel-rail force and the dynamic responses of track become bigger, so vibration reduction or vibration isolation and control measures of the track geometric irregularity should be adopted to reduce the dynamic responses of track in the crack area. The cracking of track slab has effects on the durability and lifetime of ballastless track, so it should be repaired in time.