Abstract: A rail car supplementary brake and energy reclamation and power generating system is disclosed to include a motion unit, the motion unit having a pulley block connectable to the rail car and movable along a track in the rail of the rail car, an energy accumulator unit formed of a spiral power spring mechanism and a pull rope and connected to the pulley block and adapted to reserve elastic energy when the pulley block is pulled by the rail car, a power generator, and a transmission mechanism coupling the pull rope and the spiral power spring mechanism to the power generator for driving the power generator to generate electricity when the pull rope is pulling the spiral power spring to reserve elastic energy as well as when the spiral power spring is the reserved elastic energy.