Abstract: The steel containment shell of nuclear power plant is the last barrier to prevent radioactive material from entering the exotic environment. It is very important for the safe operation of nuclear power plant. This paper mainly introduces the application of PAUT and TOFD ultrasonic testing technology to the detection of butt welds of steel containment shells with the weld reinforcement. The experimental research on the simulated test block with a certain number of typical welding defects has proven that the detection of welding defects by PAUT and TOFD ultrasonic testing shows a high detection rate, strong localization and quantitative ability. It is a reliable, efficient and economical means of inspection.