Abstract: Investigated are the causes for the early through corrosion of the Φ73 mm×5.51 mm C-90anti-sulphide corrosion tubing produced by Baoshan I＆S Corp.,Ltd.during the oil well operation.It is identified that the said early failure of the tubing resulted from the groove-like mechanical damage caused by the longitudinal abrasion by the sucker rod against the tubing inside surface and the joint corrosion by H 2 S,CO 2 and Cl.