The invention discloses a high-rise building roof rainwater power generation and elevator energy supply system. The high-rise building roof rainwater power generation and elevator energy supply system comprises a car, a pulley assembly, a dragger, a speed limiter, a pull rope, a car inner set switch, a car outer limit switch and a pair of safety tongs. An upper water tank with a rainwater collection function is arranged on a roof, and a lower water tank with a water storage function is arranged on a ground floor; an upper water pipe and a lower water pipe are arranged between the upper water tank and the lower water tank respectively; the lower water tank is provided with a mechanical water pump, and the mechanical water pump is in transmission connection with a rotating shaft of the dragger; a hydro-generator is installed on the lower water pipe. The high-rise building roof rainwater power generation and elevator energy supply system is applied to daily operation of an elevator of a high-rise building and reduces energy loss, so that a kind of clean energy is developed, and the manufacturing cost of the energy-saving elevator is reduced. A roof rainwater collection system can greatly mitigate the problems like water shortage and urban inland inundation. By collecting rainwater to generate power, a temporary power supply can be provided and personnel transfer, escape and the like are made possible in extreme weather. The water storage tank further plays a certain role in guaranteeing fire safety of the high-rise building.