Al-Si-Cu-Mg series alloys have excellent strength and toughness, but the presence of Cu-containing hardening nanoprecipitates greatly affects their corrosion resistance. For this purpose, microstructure observation and electrochemical analysis of Al-7Si-2Cu-0.6Mg alloys with different Mn alloying additions were carried out to investigate the effect of Mn addition on the microstructure and corrosion resistance of the alloys under T6 heat treatment. The results indicate that the increase in Mn addition has almost no effect on the microhardness of the alloy, but a dispersed phase can be observed in the matrix of the alloys. The corrosion resistance of the alloy tends to increase and then decrease with increasing Mn content. Compared with the base alloy, the alloy with 0.360 wt. %Mn has the best corrosion resistance, and the corrosion current density is reduced by 54%. The observation of the corrosion morphology indicates that the addition of Mn can significantly weaken the pitting corrosion trend of the alloy. The present work provides a new approach for improving the corrosion resistance of Al-Si-Cu-Mg alloys and extends the application range of these alloys.