Objective To research the influencing law of Fe element on intergranular corrosion of Al-Mg filler metal, and determine the desirable Fe content of filler metal. Methods In this paper, Al-Mg alloys with different Fe addition were prepared. The surface of alloys was modified and then immersed into 3%NaCl (mass fraction)+10 mL/L HCl aqueous solution for 24 hours at 35 ℃ to perform intergranular corrosion (IGC) experiments. Their morphologies were studied by SEM and Optical microscopy (OM). Results Maximum intergranular corrosion depths of alloys were improved from 133 μm to 179 μm by adding Fe. The intergranular corrosion resistance obviously decreased when the Fe content exceeded 0.2%. The original phase composition of alloys were transformed from α(Al)+Al3Mg2 into α(Al)+Al3Mg2+FeAl3 with increasing Fe content. The morphology of FeAl3 phase changed from skeleton into needle. The Al-Mg filler metal possessed high intergranular corrosion susceptibility with the increase of Fe-rich phases, which increased the motive force of intergranular corrosion. Conclusion The addition of Fe element could lead to structure change and thus reduce the intergranular corrosion resistance of alloys. To obtain high intergranular corrosion resistance, the Fe content in the alloy should be further reduced below 0.2%, and the lower the better.