In order to improve the riding comfort and the handling of light vehicles, many paper about semi-active suspension have been presented, but few paper talk about suspension system for light vehicles. This paper focuses on dynamic simulation and analysis of a semi-active suspension system of light vehicles. In this research dynamic models of quarter-car suspension, air spring and magnetorheological damper are built. Because the suspension components used in this research include highly nonlinear dynamic characteristics, a fuzzy logic controller and a self-tuning fuzzy logic controller are used in simulation. This research compares performances of the semi-active suspension for different road conditions and different controllers. Finally, the improvement of the riding comfort for the proposed semi-active suspension system is discussed.