Abstract: The corrosive perforation properties and causes of the welded stainless steel pipes for natural gas delivery were analyzed and discussed by means of chemical composition analysis, hardness test, metallographic examination and corrosion morphology observation, considering the using environment. The results show the area of the corrosion perforation showed a punctate distribution along longitudinal direction in weld seam of the pipes. The corrosion of the steel pipes was pitting corrosion. The high δ ferrite content in the weld seam was internal factor and contacting with dust and chlorine ion in the water was the external factor that caused corrosion perforation. The presence of residual stress in the steel pipes played a promoting role in the corrosion perforation process.