The high self-corrosion rate of Mg in aqueous electrolyte generates H2, which is the main impediment to restrict the utilization of Mg-air batteries. However, organic/inorganic hybrid electrolyte is prone to reduce the Mg degradation. Herein, the effect of different ethanol fractions in water with 0.6 M NaCl on corrosion behavior of Mg and battery discharge performances is demonstrated. The significant corrosion inhibition in a high content of ethanol (≥20 vol%) in electrolyte is attributed to the formation of a thinner, more corrosion protective layer enriched in magnesium oxide as demonstrated by scanning electron microscopy, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Contrarily, in water-based electrolyte a thick, porous and rough layer principally composed of magnesium hydroxide is formed. By varying the ethanol to water fraction in the electrolyte in full battery cell, it is shown that even a small ethanol content (≤ 5 vol%), can greatly enhance the electrochemical performances of Mg anode. Within several ethanol content, 0.5 vol% demonstrates the best performances with a limited corrosion rate and greatly improves the discharge performance and the battery lifetime. It is demonstrated here that application of inorganic/organic dual electrolyte is a promising and easy way towards a well-controlled Mg anode reactivity and improved performances of Mg-air battery.