Abstract: The roof rainfall power generation and lift energy supply system is a natural energy recycling system that utilizes high buildings to collect and store the rainwater for power generation as building energy. The system uses the potential energy provided by the water in the upper pool to generate power, and takes advantage of the liftcar down-movement to drive the pumps and thus to lift the water. The water storage will rise up to the upper pool from the pool below, thus saving energy consumption and reducing the operating costs of elevators. Through theoretical analysis, the general energy-saving efficiency of this system was derived and, according to the actual system efficiency in case studies, the feasibility of the equipment as well as its economic, social and ecological benefits was demonstrated.