In this paper, an energy saving variable damping seat suspension system is designed, manufactured and validated. A controllable electromagnetic damper (EMD), which consists of a permanent magnet synchronous motor (PMSM), a 3-phase rectifier, a metal-oxide-semiconductor field-effect transistor (MOSFET) switch module, an external resistor, a diode, and a capacitor, is designed and tested firstly. The EMD is integrated with a planetary gearbox to amplify its torque output, and both of them are installed on the centre of the scissors structure of a seat suspension. The EMD's damping property can be controlled by exerting pulse width modulation (PWM) signal with different duty cycles on the MOSFET switch module. By analysing the EMD test results and the seat suspension's kinematic, the controllable damping of the EMD is derived from 115.68 Ns/m to 669.74 Ns/m. A control method for vibration isolation is proposed considering that the generated damping force is reverse to the suspension's relative velocity, and its value is related to both the damping coefficient and the relative velocity, thus the desired control force can be partially achieved by the variable damper. The proposed variable damping seat suspension and its controller are validated on a 6-degree of freedom (6-DOF) vibration platform in both frequency domain and time domain.