Abstract: Nuclear power equipment-steel containment vessel as a nuclear reactor radiation protection of one of the three barriers, plays a crucial role on the safety of nuclear power. Steel containment vessel of the butt weld generally requires for 100% the radiographic testing, but radiographic testing has a certain undetected rate, especially the detection rate for planar type defects (cracks, incomplete fusion) is low, and with the increase of thickness, the undetected rate of X-ray testing also increases. Through simulating a certain number of defects on the block to verify the detection between PAUT and RT, we make a conclusion that the PAUT for testing the butt weld of steel containment vessel is feasible, which may provide a reliable, efficient and economic testing method for weld quality.