The welding residual stress of reactor pressure vessel’s（RPV）supporting ring and cylinder welded mockup with a thickness of 300 mm was investigated with the finite element method,and the stress was measured with the hole-drilling method to validate the simulated result. The investigated results shows that the through-thickness radial stress distribution within the weld zone presents a self-equilibrating distribution,and the through-thickness hoop stress within the weld zone is almost tensile stress with the peak tensile stress occurring at a certain depth beneath the surfaces and a minimum stress appears near the mid-thickness. The location where the minimum hoop and radial stress appears at the weld centerline is decided by the weld metal height of the second welding step for the welding procedure used in the present study. In addition,a large stress change occurs near the top surface of the weld metal after the first welding step due to the strong stiffness of the mockups.