Abstract: We have proposed a reliability test method for PAUT inspection of semi-automatically and manually welded pipe girth welds. Design and production of artificial simulation of natural defects and a large number of comparison tests such as PAUT and AUT were carried out. Through the macro slicing production and sample statistical analysis, the POD curve of the PAUT pipe girth welds defect detection and the POS curve of the quantitative ability evaluation were established, and the reliability of the PAUT girth weld inspection was further analyzed using actual data. The data results show that the PAUT has a high detection rate, the defect size of 90% detection rate at 95% confidence is 0.92 mm. The quantitative analysis results obtained by the -6 dB altimetric method shall produce large errors of average being 2.94 mm and the standard deviation being 1.37 mm. The measured defect size is generally overvalued with large dispersion, and the quantitative method therefore still needs improvement.