Abstract: The fracture accidents of Φ88.9 mm×6.45 mm 110S tubing in a oil well are thoroughly investigated and studied, the samples of four pieces of the fractured tubing which are matched with each other in two to two are analyzed and their fracture morphology, geometric parameters of tubing body, physical and chemical properties, metallographic structure and corrosion products are also tested and analyzed. The test results show that the physical and chemical properties of Φ88.9 mm×6.45 mm 110S tubing all meet the requirements of API Spec 5CT and users.The fracture mechanism of tubing is subject to H₂S stress corrosion cracking so it is recommended to strengthen the on-site H₂S detection and to use suitable H₂S resistant tubing.