<p>The circumferential welding as the most common connection way of the gathering pipeline often faces the risk of failure over time, leading to significant safety and environmental accidents. In order to determine the reason for the circumferential welding cracking in a shale gas gathering pipeline, the macroscopic morphology, physical and chemical properties, fracture morphology and composition of the failed pipe were analyzed by the macroscopic inspection, mechanical test, scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS). The results show that the chemical elements and metallographic structure of the circumferential welding of the gathering pipeline are not abnormal. There are different degrees of wrong edges in the circumferential welding, so the stress concentration exists in the weld toe. It is found that the crack originated from the corrosion pit of the weld toe and extended in multiple directions along the heat-affected zone, which is a typical brittle intergranular fracture characteristic. A large number of corrosion product detected S element is observed in weld cracks. It is worth noting that the hydrogen sulfide (H₂S) is not detected in the gas phase, and these sulfur elements should be derived from sulfur ions in water. Therefore, the circumferential welding cracking is caused by the stress corrosion cracking caused by the sulfur element in the acidic medium.</p>