The research of the nonlinear dynamic vibration of moving vehicle system, bing excited by the incentives of the road roughness, which can be reveal the complex mechanism of and improve the dynamic performance is of important theoretical significance and engineering value. First of all, based on the nonlinear motion characteristics, two degrees of freedom nonlinear vibration system with the translational motion of the up and down and pitch angle around the center of mass and the nonlinear differential equation of the vehicle dynamics mode established derived by using though Lagrange equation. The nonlinear restoring force, and the potential energy curve characteristics and stability of equilibrium point are analyzed. Secondly, for the free vibration, the amplitude ratio of the linear approximation system and the amplitude frequency curve characteristics of the nonlinear approximate system are analyzed. Finally, for forced vibration, a numerical method is used to obtain the complex nonlinear response of amplitude velocityaffect by damping, amplitude and wavelenth of road. The results show that the vehicle dynamics model has complex nonlinear dynamic characteristics, which provides a theoretical reference for providing parameter design and revealing the complex vibration mechanism of vehicle system.