Abstract: The leakage cause of TP304 stainless steel tube in gland steam condenser of USC units was investigated by means of macroscopic observation, chemical composition analysis, tensile test, flattening test, intergranular corrosion test, metallographic examination, SEM and EDS analysis. The results showed that the leakage of TP304 stainless steel tube was caused by stress corrosion under the joint action of surface residual stress and corrosive medium Cl-, S2- in steam. For this, preventive measures, such as relieving surface residual stress, strictly controlling boiler steam-water quality, reducing the content of harmful irons, have been put forward.