Abstract: Active magnetic bearing (AMB) is the best choice for the supporting structure of a high-speed flywheel energy storage system due to its no contact, no wear, no need of lubrication and dynamic adjustable. Differential control method is widely applied to the control system of an AMB flywheel rotor system. In this control method, the two opposing electromagnets on the same degree of freedom have the same constant bias current, and the sums of the bias current and control current are used to drive the two electromagnetic coils. With the existence of the constant bias current, even in no load conditions, there exists always power consumption. In response to this concern, an AMB control method, called adaptive variable bias control, is presented in this paper. In the new control method proposed, the bias current varies with the control current, and the magnitude of the bias current is equal to the absolute value of the control current. Then stability of the new control method is analyzed by control theory. Finally, the control performances of the new control method proposed are investigated by simulations. The results show that, the adaptive variable bias control method can reduce the power loss, be nominally stable, and provide the control performances similar to conventional differential control method.