Abstract: The V150 high strength drill pipe was pierced in the disappearance area of thickening transition zone during the service in a vertical well. The failure analysis of drill pipe was carried out by macromorphology observation, magnetic particle inspection, micromorphology observation, chemical composition analysis, mechanical property testing, finite element analysis. The results show that the piercing cause of the drill pipe was corrosion fatigue. The drilling fluid contained dissolved oxygen and a certain content of Cl^-, and the pH was low; serious oxygen corrosion occurred because of the stress concentration in the drilling pipe thickening transition zone, and dense pits were formed in the circumferential distribution. The drilling pipe jumped seriously during service, and the periodic vibration led to the periodic change of large stress concentration effect at the bottom of pit in the disappearance area of the thickening transition zone of drilling pipe; the drill pipe resonance phenomenon occurred, which intensified the initiation and propagation of fatigue cracks at the bottom of pit, and finally led to the piercing of drilling pipe.