Magnetic damping pendulum image formation causes Electromagnetic damping pendulum representation derived from the principle of electromagnetic induction. The microscopic appearance is: when the closed conductor and magnet relative movement occurs, the electromagnetic resistance between the two, to prevent relative movement. This representation can explain with Lenz's Law: the closed conductor and magnet magnetic line cutting motion, because the magnetic flux closed conductor penetrating changes occur, conductor induced current, relative movement that occurred in this current magnetic field will prevent both. The drag force is proportional to the magnetic induction intensity, magnet relative velocity and other physical quantities. Electromagnetic damping pendulum representation is widely used in the occasions need stable friction force and braking force, such as the watt hour meter, electromagnetic brake machine, even maglev. Dongguan Jincheng Industrial Co., Ltd. is a research and development, manufacturing, sale of tension control, magnetic damper, as one of the professional manufacturers, the main production: tension device series, magnetic damper series, tension device, magnetic damper, magnetic damper damper, damper, and other goods. Www.www.swlawyer.org.cn For simply and reliably increase the system stability, restrain rotor resonance peak. Presents a new passive electromagnetic damper. Its structure is similar to the electromagnetic bearing. But without the closed-loop control, using the DC operation. Through the analysis, the electromagnetic damping swing phase ripple current and rotor coil in the rotor eddy displacement because when changing magnetic field and the occurrence of the difference between the damping is caused, the calculating formula of the fluctuating current, damping coefficient. The experimental results show that the electromagnetic damping pendulum supply damping can effectively suppress the resonance amplitude.