The vehicle is simplified as the four-freedom vibrating model. The road is supposed as the Euler Beam on the Kelvin base. And then by the dynamic tire stress, the dynamic model and functions of the vehicle-road coupled system are derived. The functions are been divided with the compatibility deformation condition between the road and the tire, and solved with mode synthesis method and New-mark method. The results indicate that the effects of the tire-subsystem on the road can be ignored. However, its effects on the vehicle are very large. And the effects of the acceleration, initial speed and roughness of road on the vehicle are also analyzed.