Abstract: The effects of Mn on the microstructure and properties of Al-0.91Mg-0.81Si-1.02Cu-xMn-0.2Zr-0.02Sr aluminum alloy were investigated by optical microscopy, scanning electron microscopy, hardness test and tensile test. The results show that the increase of the Mn element content reduces the equiaxedness of the alloy grains while significantly refines the alloy grains.When the content of added Mn is 0.7%, the grain size of the alloy does not change much with further addition of Mn, but the tensile strength of the alloy decreases. Mn element can greatly improve the resistance of the alloy to intergranular corrosion. Considering the effect of Mn element on the tensile properties, grain size and intergranular corrosion resistance of the alloy, it is reasonable to add about 0.7% Mn to the alloy.