An active suspension system of a vehicle has a feed back control system for controlling four suspensions for the four wheels to maintain a reference vehicle height responsive to detected vertical relative displacements between the wheels and the vehicle body at said suspensions, and a feed forward control system for controlling the suspension to reduce pitching of the vehicle responsive to detected longitudinal acceleration. There is further provided a circuit for changing the reference vehicle height which is responsive to the absolute value of the detected longitudinal acceleration or deceleration for reducing the reference vehicle height with increase of the absolute value so that the vehicle body is lowered while the pitching is maintained at a predetermined value so as to obtain better driver's sensation during vehicle acceleration and deceleration and to improve the performance of acceleration and deceleration.