The invention discloses a low-grade heat energy recycling device and relates to the field of the low-grade heat energy recycling technology. The low-grade heat energy recycling device comprises a heat exchanger I, a compressor pump, a heat exchanger II, an expansion valve and a water temperature constant control system, wherein the water temperature constant control system comprises a hot water storage tank, a water temperature controller, a temperature sensor, a cold water mixing valve, a cold water and hot water mixer, an electrical heater and a cold water storage tank. According to the low-grade heat energy recycling device, heat in low-grade heat energy is absorbed by an evaporator of the heat exchanger I, is transferred by the compressor pump and a condenser of the heat exchanger II and then is output in the form of hot water, the temperature of the obtained hot water is regulated through the hot water storage tank and the water temperature controller, and then hot water with the constant temperature can be supplied to a user. The low-grade heat energy recycling device has the advantages that cyclic utilization of the low-grade heat energy is achieved and output heat is stable.