Abstract: The cracking reason of 1Cr18Ni9Ti stainless steel oil pipeline was investigated by means of chemical composition analysis, macroscopic inspection, metallographic examination and fracture analysis. The results showed that the cracking on stainless pipe belonged to stress corrosion cracking. Crack initiated from the outer surface of pipe and expanded to the inner surface of pipe. The cracking reason was that corrosive medium including elements of Cl,S and O in industrial water deposited on the outer surface of pipe. Because of the interaction of pipe pressure and corrosive medium, stress corrosion cracking occurred in stainless steel pipe.