Abstract: In order to investigate the distribution of welding residual stress in heavy-section SA508-3 steel welded joint and the effect of post-weld heat treatment (PWHT) on distribution of residual stress, the welding and PWHT process was numerically simulated by using finite element method. The simulated results show that PWHT had little effect on the distribution of welding residual stress, but PWHT could significantly reduce the welding residual stress. The maximum amplitude of longitudinal stress decreased by 72%, and the maximum amplitude of transverse stress reduced by 70%. Quasi-stable stress region distributed in the welded joint. The residual stress inside the welded joint was the smallest, followed by that on the upper surface, and the residual stress on the bottom surface of welded joint was the greatest. The simulated residual stress agreed well with the experimental results, indicating that the calculation model and method are reliable and can guide the practical PWHT of SA508-3 steel plates.