In addition to increment of the vehicle sprung mass, the main physical effects of addition of CNG tank to the vehicle are the longitudinal and height displacement of center of gravity, which have the most influences on the handling, braking, roll stability and spin stability of the vehicle. Increment of CNG tank mass to the sprung mass of the vehicle increases the vehicle under-steer gradient, decreases roll stability and increases stability of vehicle on the straight line and S bends; meanwhile climbing ability of the front wheels drive vehicle is decreased. Due to increment of CNG tank to the sprung mass of the vehicle, the probability of vehicle spinout is increased, when driver brakes severely. First, we investigate the main components of vehicle dynamic performances which are affected by increment of CNG tank have been clarified. By using the available data and dominated equations on vehicle dynamic behavior, the vehicle performance has been analyzed.