Abstract: The circumferential weld connecting the long-neck flange and pipeline of high-pressure gas injection lines in underground natural gas storage reservoirs serves in harsh environments with high-pressure gas, various complex stresses, and corrosive media. If there are quality issues, it could lead to serious accidents such as gas leakage and explosion. Compared to traditional RT and UT detection methods, PAUT+TOFD detection technology has certain advantages in defect detection capability, detection accuracy, resolution, efficiency, etc. Combined with engineering practice, experimental research on the PAUT+TOFD detection process was conducted from aspects such as welding joint structural characteristics, comparative and simulated test block fabrication, detection process design, and verification. The verification results showed that this technology could provide reliable technical support for the periodic inspection of circumferential welds of long-neck flanges in high-pressure gas injection lines of natural gas storage reservoirs.