Welding residual plastic strains and residual stresses are the product of complicated nonlinear behaviors of the structures during welding. The residual strains and stresses for stiffened stainless steel structure and welding fatigue analysis are studied in this paper. The three-dimensional transient temperature field is analyzed by FEM first. Doing the welding experiment for fundamental model is to verify the numerical results, the infrared thermograph is used to follow and record the whole process. The results of FEM are supported by experimental data. Then, the elastic-plastic-model is established to analyze the residual strains and stresses. Based on the stresses, loading and fatigue factors, according to Miner fatigue damage law, some fatigue behaviors such as fatigue life and remaining life are obtained.