The invention provides a heat supply system. The heat supply system comprises a first heat exchange circulation, a second heat exchange circulation, a third heat exchange circulation and a fourth heatexchange circulation, wherein the first heat exchange circulation is connected with the second heat exchange circulation, the second heat exchange circulation is connected with the third heat exchange circulation, and the third heat exchange circulation is connected with the fourth heat exchange circulation. According to the heat supply system, the first heat exchange cycle, the second heat exchange circulation, the third heat exchange circulation and the fourth heat exchange circulation are arranged, so that the circulation heating of the heat is achieved, meanwhile, an air-cooled heat pumpunit and a high-temperature heat pump unit are used simultaneously for providing heat energy, an energy storage water tank is arranged for storing energy so that energy storage can be carried out during the electricity valley period at night, and energy storage is stopped and heating can be carried out during the power consumption peak period in the daytime, then the problem of electric power waste is effectively solved, and meanwhile, and the cost are saved.