The discharge behaviour of Mg-Al-Pb and Mg-Al-Pb-In alloys in 3.5wt.% NaCl solution is investigated by electrochemical techniques, and compared with that of pure magnesium. The results show that Mg-Al-Pb-In alloy provides a more negative potential and exhibits a higher utilization efficiency in contrast with Mg-Al-Pb alloy and pure magnesium during the half-cell test at a large current density, and gives desirable discharge performance when used as anode for Mg- air battery. The peak power density of the Mg-air battery with Mg-Al-Pb-In anode is 94.5mW cm−2, which is comparable with those of Mg-H2O2 semi-fuel batteries. Moreover, the activation mechanism of Mg-Al-Pb-In alloy during the discharge process is also analyzed.