The invention relates to the technical field of water treatment, in particular to a reverse osmosis (RO) water purifier waste water recycling system. The system can effectively solve the problem that waste water is hard to utilize and meanwhile can reduce the water making cost. The system structurally comprises a water storage container. The water storage container is provided with a water inlet and a water outlet. The water inlet is connected with a waste water pipe of a water purifier. The water outlet is connected with a faucet through a drainage pipe. A water level sensor is arranged in the water storage container and connected with a water level controller through a connecting circuit. The water level controller is connected with the connecting circuit of the water purifier. The water storage container is closed. An exhaust valve is fixedly arranged on the top of the water storage container. A water level display screen is fixedly arranged on the outer surface of the water storage container and electrically connected with the water level controller. According to the system, the water making cost is reduced, waste of a large number of water resources is avoided, and the system is easy to operate, convenient to use and applicable to RO water purifier waste water recycling.