Abstract: This paper presented the basic working principle of closed and open two phase thermosyphones briefly at first. Then it described each kind of heat recovery method of heat pipe heat exchangers used in small industrial boiler: heating water (including producing boiling water), heating air and heating both water and air. These heat pipe exchangers have such advantages as small volume, lingt weight, simple structure, small pressure drop on gas sicd, good property of enduring low temperature corrosion, flexiable and easy to arrang, and so on. This paper described the applicational conditions of heat pipe heat exchanger used in three small industrial boilers in Fu- Yang of Zhejiang Province. The capacity of the boilers are 1t/h, 2t/h, and 4t/h. The methodes of heat recovery is heating air, heating water, heating both air and water. The efficiency of the boilers can be raised for more than 3～4%, and the recovery time of investment is one year or less. Heat pipe heat exchanger has good economic and social effects, and has a wide pespective of application in city or country enterprises.