Abstract: The keyhole TIG (K-TIG) welding process is adopted to realize the single side welding and double side forming of 10 mm thick C-276 alloy plate. The weld cross section has no defects such as porosity, incomplete fusion and crack. The structure of the weld zone is mainly elongated columnar crystal and equiaxed crystal, and a small amount of precipitates are distributed at the grain boundary. The intergranular corrosion test is carried out by ASTM G28A method. The results show that the average corrosion rate of the weld is 4.418 mm/a, and its intergranular corrosion resistance of the weld is good. The average tensile strength of the joint is 735.5 MPa, and the fracture position is in the base metal. A large number of the fine equiaxial dimples are distributed on the tensile fracture surface, which is typical ductile fracture, and the joint has good toughness. No cracks are found by side bending test. The hardness values of the base metal, heat affected zone and weld seam of the joint have little difference, and the hardness of the joint is in good consistence.