Abstract: A tee elbow of stainless steel was leaked during operation. By means of chemical composition analysis, metallographic examination, mechanical property testing, SEM and EDS analysis, intercrystalline corrosion test and so on, the cracking cause of tee elbow was analyzed. The results showed that there was corrosive medium existed in the environment where tee elbow worked; the environmental medium, residual stress and operating stress led to intergranular stress corrosion cracking on the tee elbow.