Abstract: Washout failure of a 110 grade, φ88.9 mm×6.45 mm super-13Cr martensitic stainless steel tubing was analyzed by means of macro analysis, chemical compositions analysis, mechanical property test, metallographic examination and SEM fracture analysis. The results show that the essence of failure was chloride stress corrosion cracking occurred on the tubing. The crack originated from the bottom of pits laid on the outer surface of the tubing, and developed from outer surface to inner surface to form the pierced channel until it penetrated the wall thickness. Thus, high pressure fluid flowed out from the inside of tubing and led to the piercing hole produced.