Abstract: The reason of cracking of 304 stainless steel hydrogen production heat exchanger coil was found out through analysis of macrostructure, microstructure, chemical composition, morphology of fracture and chemical composition of corrosion products. The results show that, it was stress corrosion cracking of 304 stainless steel coil. Working stress of the coil and dissolved oxygen in the shell side steam led to the cracking of coil. It was suggested that adopting Incoloy 800 Fe-Ni corrosion resistant alloy to replace 304 stainless steel as material of hydrogen production heat exchanger coil.