In this research, Mg-Ca binary alloys are evaluated as anode material candidates for primary Mg-air batteries. The effect of Ca content on self-corrosion and discharge performance of Mg anode is investigated through microstructure characterization, electrochemical measurements and half-cell discharge tests. Then the composition of Mg-Ca alloys is optimized in terms of reduced self-corrosion and improved discharge performance. The basic characteristics of Mg-air batteries with optimized Mg-Ca alloy as anode are tested and compared to those based on high purity Mg and defined commercial Mg alloys. The results show that Mg-0.1 wt. % Ca alloy has the best self-corrosion behavior and discharge performance among all prepared Mg-Ca alloys. The Mg-air battery with Mg-0.1 wt. % Ca alloy as anode offers higher cell voltage and specific energy than those based on high purity Mg, AM50 and AZ31 alloys.