Truck suspension system could alleviate vertical vibration as well as pavement deterioration effectively. Multiple methods are employed to promote truck performance, such as the optimal passive damping method, semi-active control and active control. With the purpose of improving ride comfort and road friendliness simultaneously, semi-active suspension systems based on fuzzy control algorithm are investigated in this paper. At first, a ten-DOF whole vehicle dynamic model was developed based on Matlab/Simulink, proper passive air suspensions were chosen to replace the original rear leaf suspensions. As time lag between demanded and achieved damping force of semi-active dampers was considered, effects of the optimal passive damping method and semi-active fuzzy damping control were analyzed and compared. Simulation results indicate that the latter one is more effective in reducing vertical body acceleration and tire dynamic forces. © 2010 IEEE.