Abstract: The fracture phenomenon of the valve body stud of the high-pressure multi-phase flowmeter connected to the isolation ball valve in an offshore gas field occurred. The fracture causes of the stud were analyzed by macroscopic observation, chemical composition analysis, fracture surface analysis, hardness test, metallographic examination and other methods. The results show that under the action of marine atmospheric environment and pre-tightening force, the stress corrosion cracking of the stud occured. The micro-cracks initiated in the radial direction of the stud, and the cracks grew and expanded along the radial direction. When the crack size reached a certain degree, the stud broke as a whole.