A low impedance power disc is provided. The power disc is connected to a crankshaft of an engine, and includes a rotor, a connecting shaft, and a permanent magnet. The rotor is disposed separately from the permanent magnet. The connecting shaft is locked inside the rotor. A unidirectional bearing is provided and fitted on the connecting shaft. The permanent magnet is fitted on the unidirectional bearing. When the engine is running, the rotor and the permanent magnet are rotated at the same speed to generate electricity and supply the electricity to the vehicle and to charge the battery. When the engine decelerates, the rotor and the connecting shaft are decelerated synchronously with the engine, while the permanent magnet and the unidirectional bearing are continuously rotated at the speedbefore deceleration in order to facilitate the engine to accelerate again, so that the rotor of the disc can be rotated at the rotating speed before deceleration and the engine performance and the generation efficiency can be improved.