Abstract: Repair welding tests of SMA490BW welded joint with different depth defects were carried out. The microstructure, residual stress and mechanical properties of the repaired joints were studied. The results show that the repair welding for defects with the depth of 2-6 mm could not affect the weld structure, which is composed of proeutectoid ferrite, acicular ferrite and granular bainite. Repair welding has a thermal effect on the original weld and normalized fine grain structure is formed.The hardness of the weld zone of the repair welded joint is lower than that of the initial welded joint, and the repair welding has little effect on the tensile properties of the joints, but the impact properties of the repair welded joints are better than that of the initial joint.With the increase of defect depth, the number of repair welding passes increases, which makes the joint and the base metal suffer from multiple thermal cycles and affects the residual stress distribution of the joint.When the repair welding depth is 6 mm, the longitudinal residual stress near the weld exceeds the yield strength of the base metal itself, and the heat treatment is no longer carried out after the actual welding repair, therefore, it is not recommended to repair the defects with the depth more than 6 mm.