The effect of Ca and Mn additions on cast ability, ignition temperature, and electrochemical properties has been investigated in the as-cast magnesium alloys. Not only the remarkable improvement of electrochemical properties but also the ignition prevention of magnesium alloys during melting and casting is achieved by small addition of Ca and Mn into Mg. Flow length of the specimens decrease with an increase of Ca content. Serious decrease of flow ability in Mg melt is observed in Mg-1.31wt%Ca alloy. However, flow length of Mg-Ca alloys is negligibly influenced by small amounts of Mn addition. The improved performance of Mg-Ca alloys is attributed to the homogeneous and refined microstructures with extremely electronegative potential of Ca. It is considered from that serious reduction in flow length of Mg-1.31wt%Ca alloy is due to cast from large solidification interval.