Abstract: By means of Finite Element Method (FEM), the change of internal stress in equal-matching and under-matching butt joint of high strength steel on the condition of tensile load after welding was investigated. The results show that the stress level of both weld and base metal in equal-matching and in under-matching butt joint have continued to increase, during transverse and longitudinal tensile loads after welding reached the critical load of failure. But compared with distal base metal, the stress of the welding zone and their adjacent zone increased more slowly on the basis of welding residual stress. In the end, the stress in base metal zone near the seam was significantly higher than that in the distal base metal zone, and which didn't exhibit the feature of the internal stress complete homogenization. This means that the static load strength of equal-matching welded structure of high strength steel wide plate might reduce a little by Influence of the welding residual stress, and the static load strength of under-matching welded structure of high strength steel wide plate reduced more under the reason of low strength weld seam.