Abstract: The paper focuses on the simulation of forming process of welding residual stress and effect of explosion shock waves on welding residual stress relief. Firstly, the distribution of welding residual stress on butt joint was numerically simulated with indirectly coupled temperature field and stress field. Secondly, the effect of explosion shock waves, produced by plastic strip-like explosive, on welding residual stresses was predicted with coupled lagrange-ALE algorithm. It implicates that explosion treatment can effectively reduce welding residual stress with little deformation, which doesn't deteriorate structural dimensions and achieve 80% of stress reduction.