Abstract: Based on the requirements of DNVGL-ST-F101-2017 and in combination with the characteristics of U-groove welds of submarine pipelines, two types of pipeline were selected for the test, in which the diameter of one pipeline is 168 mm with its wall thickness being 18.6 mm, and the diameter of the other one is 508 mm with its wall thickness being 31.8 mm. A series of defects including non-fusion, porosity and inter-run etc were made for the two types of pipeline, and the locations of welding defects were distributed in the root, hot pass, filling and surface of the weld. TOFD(time of flight diffraction) and PAUT(phased array ultrasonic testing) technique were used to scan the test welds, and furthermore evaluation of the defects, sizing and metallographic test for all the defects were carried out in order to determine the sizing result deviation. By comparing the differences between TOFD and PAUT measurement results and metallographic test results, the accuracy and reliability of TOFD and PAUT testing can thus be determined.