At present, the radial vibration of a rotor is the most significant problem demanded to overcome in a single-direction active magnetic bearing system. A new 4pole-electromagnet is proposed in this paper. Two controlled currents will be applied to the opposite poles on the electromagnet. It is utilized to overcome the torque which causes the period vibration of the rotor. The torque results from the electromagnetic force interaction between a permanent and an electromagnet. The structure and the magnetic circuits of the electromagnetic actuator will be analyzed by ANSOFT/EM3D. The material of electromagnetic actuator should have a small coercive force and a high permeability.