Abstract: In this paper, the structural characteristics of the non-radial pipe-plate welded joints for containment penetrations in AP1000 PWR nuclear power plants are presented, and the key points and difficulties of ultrasonic testing process are analyzed. By establishing a unified defect positioning coordinate system and combining the geometric characteristics of the testing component, the h-value (Distance of the maximum of defects echo amplitude from the outer wall of the casing) is derived from the comprehensive analysis. The aim of the research is to provide ultrasonic testing with an effective method for the accurate identification and localization of defects in such welded joints. It can also provide effective measures for the ultrasonic testing of some technical restricted areas of this type of welded joints.