In this paper, we describe a new semi-active suspension system to realize the “skyhook” principle. The “skyhook” damping principle is a basic concept of the semi-active suspension control for improving vehicle stability and ride comfort. Recently, several practical methods have been proposed to realized the “skyhook” damping principle. We understand that these proposed systems still have room for improvements in terms of system complexity. Therefore, we have developed a semi-active suspension control system with four smart actuators. The smart actuator has a controller IC on it into which the acceleration sensor, signal processing circuit and actuator driver are integrated.