In order to obtain the boundary conditions for the launch stability and the launch safety of the vehicle weapon system, the power spectrum density function is used to simulation the random excitation of the road surface, and the mathematical model is established and its accuracy is verified. A multi degree of freedom vibration model of vehicle weapon is established. The dynamic simulation of the vehicle is carried out based on the virtual prototyping technology, study on the dynamic response of the weapon system under different road conditions and moving speed. Research results shows that the road surface accord with the real road and initial disturbance of the missile is too large when the vehicle speed is high and the road surface is poor.