This paper presents a new correlated methodology for engineers to develop a specific vehicle-Unimog associated with a unique structure of movement transmission. A complicated multi-body dynamic model which includes the front/rear axle suspension with thrust tube and coil springs, the steering system, tire and road exciting model is established based on the virtual reality (VR) technology. The topology and kinematics relation of the whole system are analyzed firstly, then the proper constrain pairs are applied among them to satisfy the amazing flexibility and ride comfort of the real vehicle. To more accurately model the real system, some key parameters are acquired by the way of experiment and prediction, respectively. And a triangle function method which combined the inverse Fourier and discrete random producer is proposed based on the standard PSD (power spectrum density). Finally, the ride performance has been evaluated on the random road by simulation and field test. The results show that the applied constraint of the model is correct and the kinematics relation matches the actual condition well. The consistency trends both in time and frequency domain for virtual and field test result show that the established model is effective.