Heat exchange unit is designed to automatically and continuously convert the heat provided by one-off thermal network into the heat for domestic water and heating water needed by users. It is composed of plate heat exchanger, circulation pump, water supplementing pump, thermometer, pressure gauge as well as various sensors, pipelines and valves. It can be mounted with water supplementing system, pressure stabilizing system, frequency-changing flow control system, heat measuring system and online communication control system according to customers’ requirements.