Abstract: The article introduces the operating principle of the improved heat pipe exchanger (two-phase hemi-open type)and the calculating method of its heat efficiency, and cites three examples of this kind. The heat pipe exchanger works in the way of high heat transfer efficiency, low pressure loss with a compact structure, wide application range and a low maintenance cost. However, the dew point corrosion is the major defect in this kind of heater. It is pointed out that this heater can recover flue gas used heat of all kinds of heating equipments by means of improving its performance in practice.