Abstract: The behavior of H₂S stress corrosion cracking of coiled tubing was investigated,the fracture morphology was observed by scanning electron microscope,and the elemental composition of fracture was analyzed by energy disperse spectroscopy.The fracture mechanism was analyzed from the aspects of environment factor,material structure and chemical constitution.The results show that the base metal is insensitive to stress corrosion,and the weld is the weak region of stress corrosion.The weld fracture can be subdivided into four periods:crack incubation period,crack development period,crack rapid growth period with a smoother fractured surface and eventual failure period.The effect of stress change on sulfide stress corrosion cracking is relatively less in the yield strength of 72%-90%.The weld defect,segregation and inclusion are the main factors that make the coiled tubing have low resistance to hydrogen sulfide corrosion.