The mechanical properties of magnesium alloys at both ambient and elevated temperatures can be improved with the existence of Mg2Si phase in the matrix. However, these properties can be deteriorated if the Mg2Si phase is of coarse Chinese script type. Effects of the silicocalcium addition on the microstructure and properties of an Mg-6Al-0.5Mn alloy (AM60) were studied. The microstructure of the alloy with the addition of silicocalcium is featured with dispersedly distributed small polygonal type Mg2Si phases. The microhardness, tensile strength,percentage elongation and toughness of as-cast AM60+1.0Si-Ca alloy are 20%, 13.3%, 28.5% and 50% higher than these of AM60 alloy respectively. Further corrosion measurements showed that the silicocalcium-modified AM60 alloy increases the corrosion potential by 0.04V and decreases the lost weight corrosion rate by 45%.