Abstract: In order to study the corrosion mechanism of the in-service heat exchanger tube bundle so as to guarantee the operation reliability thereof,the specimens of 20# steel and 304 and 316L stainless steels are put into the shell pass raw water,the heat exchange steam and the mixed liquids at the bottom of heat tower for 160 days. Then the uniform corrosion rates of the specimens are tested,their morphologies are observed,and their corrosion products are analyzed with XRD method. The results show that the corrosion mechanism of the heat exchange tube bundle is oxygen corrosion;and the 316L stainless steel displays an excellent corrosion resistance during the test. Accordingly it is suggested to select the 316L stainless steel as the material of the heat exchange tube bundle,and to periodically clean dirt together with use of the scale inhibiter in a bid to meet the anti-corrosion requirement for the said tube bundle.