Abstract: To clarify the corrosion resistance of high entropy alloy welded joint, the eutectic dual-phase high entropy alloy AlCoCrFeNi_2.1 was welded by electron beam welding (EBW), and the corrosion resistance of the joint was studied by electrochemical corrosion method. The results show that the self-corrosion potential of weld zone (FZ) is about 0.16 V higher than the one of base metal (BM), the corrosion resistance is enhanced, and the self-corrosion current is reduced by one order of magnitude, and the corrosion rate is greatly reduced. The corrosion pits in the base metal area of the welded joint are expanding in depth, while the corrosion pits in the weld area are expanding horizontally, showing obvious phase selective corrosion. The grains in the weld area are obviously refined, the hardness is stable and slightly increased, and the two-phase distribution presents a dense "network" trend, which is more uniform than the macro distribution of elements in the base metal. These contributes for enhancing the corrosion resistance and penetration of welded joints.