Abstract: In order to improve the handling stability and the ride performance of multi-axle vehicle, through building a 5+2n degree of freedom multi-axle vehicle dynamic model, a LQG controller was designed. According to the simulation test, the responses of active suspension vehicle and passive suspension vehicle to the performance index of the step signal at low and high speed were analyzed and compared. Results of the analysis indicated that the peak side angle decreased by 0.03 rad, the peak vehicle yaw rate, by 0.1 rad/s, the peak rolling angle, by 0.015 rad, the peak pitching angle, by 0.015 rad, the peak vehicle vertical acceleration, by 0.3 m/s2 and the peak tire dynamic displacement, by 0.009 m, comparing active suspension vehicle with passive suspension vehicle at low-speed. At high-speed, the peak of performance indexes above respectively decreased by 0.095 rad, 0.4 rad/s, 0.075 rad, 0.09 rad, 2.1 m/s2 and 0.018 m. The handling stability and the ride performance of active suspension vehicle are improved significantly comparing with passive suspension vehicle.