The full vehicle dynamics model of a threeaxle heavyduty vehicle with semiactive suspensions was established, and the optimal control for vehicle ride comfort was studied. An integral balance suspension and a practical cab model were used to build the vehicle dynamics model.The assembly decomposition method was used to calculate the rotational inertia of the vehicle. For the semiactive suspension system, three fuzzy controllers were designed by employing the vertical velocity, pitch angular velocity side inclination angular velocity as well as their corresponding change rates as input signals,respectively. The control strategy was simulated by using MATLAB/Simulink, which was compared with the passivesuspension vehiclea model. The results showed that the vibrations of both the vehicle body and cab are attenuated substantially by using the proposed control strategy, and thus the ride comfort of the vehicle is improved effectively.