The invention relates to a supercooling device of central air-conditioner, belonging to air-conditioner adjusting technological area, solving superheating of compressor by cool medium flowing into compressor in conventional supercooling device. The technological scheme of problem comprises supercooling device which decreases the temperature of cool medium as heat energy is exchanged with cool medium of inside heat exchanger from outside heat exchanger; recycling pipe, by which drainage port of the supercooling device is connected with cool medium pipe at the inputting side of fluid storage tank; superheating pipe, by which partial cool medium flowing along recycling pipe is transmitted to the cool medium pipe at the drainage side of compressor; and the channel set at the joint position between recycling and superheating pipes, which is controlled by temperature sensor so that the cool medium drained from supercooling device flows to the valve of recycling or superheating pipe. When thetemperature of cool medium drained from supercooling device is higher than the appropriate temperature range, the cool medium from supercooling device is transmitted to the drainage side of compressor so as to prevent high-temperature cool medium entering into compressor.