In this research, a new Mg-air battery based on Mg–14Li–1Al–0.1Ce was prepared and the battery performance was investigated by constant current discharge test. The corrosion behavior of Mg, AZ31 and Mg–Li–Al–Ce were studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The characteristics of Mg–Li–Al–Ce after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Mg–Li–Al–Ce is more active than Mg and AZ31. The self-corrosion rate is found to be in the order: Mg–Li–Al–Ce<Mg<AZ31. It has been observed that the Mg-air battery based on Mg–Li–Al–Ce offers higher operating voltage, anodic efficiency and capacity than those with Mg and AZ31. SEM and EIS results show that the discharge product of Mg–Li–Al–Ce is loosely adhered to the alloy surface, and thus Mg–Li–Al–Ce could keep high discharge activity during discharge.