Abstract: Welded joints are vulnerable sections with high incidence of corrosion failure during pipeline service. This paper studies the corrosion behavior of welded joints between Inconel 625 alloy and 316L stainless steel under seawater immersion, so as to deepen the understanding of the corrosion characteristics and action mechanism of such joints. Seawater immersion corrosion tests were carried out on Inconel 625-316L welded joints. After corrosion period, scanning electron microscopy (SEM) is used to observe the micromorphology of the corroded surface, and energy dispersive X-ray spectroscopy (EDS) is applied to analyze the elemental composition and product characteristics of the corroded surface, in order to reveal the corrosion evolution law of the joints at the micro level. The overall corrosion rate of the welded joints is significantly higher than that of monolithic 316L stainless steel. A large number of deep corrosion pits are present in the 316L region near the weld seam, and both the number and depth of corrosion pits decrease remarkably with increasing distance from the weld seam. With the increasing of corrosion time, the oxygen content on the corroded surface rises significantly, indicating an increase in oxidation products. Significant galvanic corrosion occurs in the welded joints of Inconel 625 and 316L in seawater environment, and the accumulation of oxidation products is an important microscopic manifestation of corrosion progression. The findings of this study can provide a test basis for corrosion prevention design and life evaluation of welded joints in subsea long-distance pipelines.