The invention provides a water supplementation system and an air-conditioned power generation car with the same. The water supplementation system comprises an expansion water tank and a water supplementation tank. A water outlet of the expansion water tank is used for being connected with a pipeline. The water supplementation tank communicates with the expansion water tank through a water supplementation pipeline and is used for supplementing the expansion water tank with water. By means of the water supplementation system, the problem in the prior art that a power generation device is prone to faults due to insufficient cooling water capacity of a power generation car is solved.