Abstract: Based on the FEM analysis of the distribution and variety of the stress and strains of the large-size dissimilar steel welded tube-plate structure under cyclic loading,the location of fatigue crack initiation of this structure were predicted,and low-cycle fatigue test was performed to verify the prediction and to study the cracks propagating paths.The results indicated that the weld toes linked to the two surfaces of the plate were the positions with the peak values of the maximum stress and the stress amplitude.The plastic deformations in the first loading cycle introduced the tensile-compressive repeated stress cycle at the weld toes during the subsequent loading cycles.It induced the fatigue cracks initiating at the weld toes linked to the two surfaces of the plate respectively.After initiating from the surfaces,the cracks propagated along the fusion lines with a short distance then turn into the base metal in the sections vertical to the surfaces.The depth of the crack initiating from the compressed surface was shorter than the one from the tensioned surface.