Mg-air batteries have excellent applicability in the fields of electrochemical energy storage and conversion due to their high theoretical voltage (3.09 V) and high specific energy density (6.8 kW·h/kg). Nevertheless, the high polarization and low Coulombic efficiency reduce the inherently outstanding discharge performance of the Mg anode. Alloying and plastic deformation have been utilized to overcome these drawbacks by developing novel anode materials with relatively enhanced performance. In this work, the effect of microstructural characteristics on the discharge performance and electrochemical behaviors of the extruded Mg-2Bi-0.5Ca-0.5In (mass fraction, %) alloy as an anode for Mg-air batteries have been systematically discussed. Results indicate that the extruded alloy primarily consists of complete dynamically recrystallized grains with an average grain size of (10.92 ± 0.23) μm. The texture component is mainly composed of nonbasal texture consisting of texture components of basal poles from the normal direction to extrusion direction by around 45^o-60^o. The alloy contains α-Mg, nanoscale Mg₃Bi₂ phases, and microscale Mg₂Bi₂Ca phases. Furthermore, the extruded alloy exhibits a stable discharge process and negative discharge potential of -1.628 V at 10 mA/cm² in a half-cell test. Moreover, the Mg-air battery based on the extruded alloy as an anode exhibits a high cell voltage and power density. For instance, the cell voltage and peak power density reach up to 0.72 V and 86.4 mW/cm² at 120 mA/cm², respectively, which is significantly higher than commercially accepted AZ31 and AM50 anodes for Mg-air batteries. The outstanding discharge properties are primarily attributed to the re-deposition of metallic In at the electrode surface, the weakened texture intensity, the uniform microstructure and the loose and thin discharge products film.