This work investigated and discussed the role of long-period stacking ordered (LPSO) phase on discharge performance and electrochemical behaviors of Mg-Zn-Y anode for Mg-air battery in detail. The volume fraction of LPSO phase increases with the increasing Y and Zn content. Compared with Mg-2Zn anode, Mg-Zn-Y anode with low content of LPSO phase has better discharge properties due to high open-circuit potential and low corrosion rate. However, anodes contained a high volume of LPSO phase exhibit poor corrosion resistance and discharge properties. The ZW12 alloy shows the best discharge capacity and anodic efficiency as high as 1612.9 mAh center dot g(-1) and 74.49% at the 40 mA center dot cm(-2). It also outputs a high peak specific energy 1859.15 mWh center dot g(-1) at 10 mA cm(-2), which is 37.56% higher than Mg-2Zn anode and 249.44% higher than ZW39 anode. The LPSO phase totally changes the decomposition process of Mg matrix, displaying the lamellar peeling surface in LPSO-affect zone. This lamellar peeling mode can help to take away the discharge products from the anodic surface, improving the anode performance.