Abstract: A nuclear power product made of SA508-3-1 material has repeatedly failed the drop hammer test NDT results during mechanical testing, but the impact toughness index meets the design requirements. Therefore, through a detailed analysis of the drop hammer test weld length, weld notch width, weld notch bottom height, sample type, welding heat affected zone, impact toughness-brittleness transition temperature and NDT relationship, the factors affecting the NDT results are found to provide a reference for improving the pass rate of the drop hammer test.