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In view ol the problems ol incomplete penetration and poor perlormance in the traditional method ol welding thick plate Inconel625 alloy, plasma welding technology was used to weld 8 mm thick Inconel625 alloy, and ERNiCrMo-3 welding wire was used as the lilling material to ensure molding. The microstructure and properties ol the welded joints were analyzed via Optical Microscope (OM), Scanning Electron Microscope (SEM), universal testing machine and microhardness testing machine. The results show that the welded joint has the optimal lorming and mechanical properties under the welding current ol 230 A, welding speed ol 240 mm/min, wire feeding speed ol 1 400 mm/min and plasma gas flow ol 4 L/min. The welded joints show a c Y;-shaped morphology with a wide top and a narrow bottom. The base metal area is austenite equiaxed crystal, the weld zone is mainly composed ol line cellular crystals, and the fusion line area is coarse cellular crystals grown perpendicular to the fusion line, MC carbide and Laves phase will precipitate during the welding process. The tensile strength of the joint is the highest, which can reach 811. 36 MPa, and the Iracture ol the welded joint is ductile Iracture, The hardness ol the weld zone is the highest under all parameters. As the welding heat input increases, the overall hardness of the welded joint increases. When the current reaches 240 A and 250 A, the hardness dillerence of the welded joint is small・ [ABSTRACT FROM AUTHOR]