Abstract: An active variable stiffness/damping control device is designed and manufactured, and simulated earthquake shaking table tests of the device are carried out to examine its control mechanism and effectiveness. The results of the tests show that although only a little amount of energy is inputted into the device, significant control effectiveness is obtained, and most of the time, the device works in variable damping state to reduce the vibrations of the controlled structure, which indicates that the influence of time delay is small in the device.