<p>Corrosion perforation occurred in the fourth tubing pup joint at the wellhead of a gas well experienced corrosion and perforation failure. In order to analyze the reasons for corrosion perforation failure, the following experiments were conducted, including data verification, macroscopic morphology analysis, mechanical properties, microstructure analysis of corroded areas, energy spectrum analysis and also XRD phase analysis. And a comprehensive analysis was conducted on the material properties, wellbore fluid composition, structural factors, and cavitation erosion factors that affect the corrosion failure of the tubing pup joint. Through the above experiments and analysis, it can be concluded that: 1) The chemical composition of the body and coupling, tensile strength of the body, and Charpy impact test results of the coupling meet the requirements of API Spec 5CT-2023. 2) The corrosion perforation failure of the tubing pup joint from the outer surface to the inner surface was mainly the result of the synergistic effect of turbulent flow formed by fluid erosion near the continuous pup joints and cavitation erosion formed near the wellhead. 3) The severe corrosion of the coupling was due to being bitten and damaged by the hydraulic clamp during the fastening process.</p>