Mechanical behavior and fracture process of weld specimens were analyzed by finite element method. Three-dimensional butt-weld specimen was modeled by two-dimensional approaches. Welding residual stress in the models was obtained by carrying out thermo-mechanical calculation. To take into account straight boundary lines of real weld specimen, the finite element model was constructed by using an iterative method. Cohesive zone method was applied to analyze fatigue behavior of the models.