In order to analyze the dynamics laws of special vehicle driving conditions, this paper established a six-bridge special vehicle model, which covers vertical acceleration, lateral acceleration, and lateral Angle speed, pitch Angle speed and yaw speed in the vehicle rotating motion. The translational and rotational motion of the vehicle under driving conditions were studied. A vertical model is built to study vertical acceleration in translational motion, pitch Angle speed and lateral Angle speed in rotational motion, and a lateral model is built to study lateral acceleration in translational motion and yaw speed in rotational motion. The longitudinal speed of the longitudinal model is introduced, and the longitudinal speed is dynamically coupled with the vertical model and the lateral model through the tire model. A special vehicle dynamic coupling model was established, and the road excitation and vehicle steering shaft Angle input generated by random white noise method were used to analyze the dynamic coupling model, and the vehicle stability under the driving conditions of the special vehicle was studied.