Abstract: The arc spot welding was used to join 3 mm and 5 mm thick 0Cr18Ni9 stainless steel plates. Welding current and holding time were optimized to get the best match between the microstructure and mechanical properties. The welding defects, microstructures and mechanical properties were analyzed by X-Ray detection, optical microscopy (OM) and electronic universal testing machine, respectively. The results showed that the joints by arc spot welding presented a mushroom shape, which smoothly transited with the substrate, while no holes, cracks and other macro defects were observed. The weld penetration and nugget diameter, and shear resistance stress of the joints increased with the first and second currents. Under the optimized parameters, the weld penetration, nugget diameter and shear resistance stress respectively reached 4.07 mm, 7.73 mm and 23.65 kN, which satisfied the demands of the production.