Abstract: A patch plate welding test was carried out on 304L stainless steel by acctomatic tungsten inert gas (TIG) welding combined with swing welding under different swing amplitudes (2, 3, 4 mm) with ER316L welding wires. The influence of welding torch swing amplitude on the microstructure, phase composition, microhardness, and corrosion resistance of weld seam of the joint was investigated. The results show that the microstructure of weld seam of the joint under different swing amplitudes was mainly composed of γ-austenite and δ-ferrite. With the increase of swing amplitude, the diffraction peak intensity of (111) crystal plane of γ phase decreased, and the diffraction peak intensity of (110) crystal plane of δ phase increased. Under large swing amplitudes (3, 4 mm), the δ-ferrite was distributed in a skeletal shape along the grain boundaries of the γ-austenite columnar crystal/equiaxed crystal. With the increase of swing amplitude, the content of δ-ferrite increased, the content of γ-austenite decreased and the grains of γ-austenite were refined, resulting in the increase of hardness of weld seam, the decrease of self corrosion potential, the increase of self corrosion current density, and the decrease of corrosion resistance.