Abstract: Three kinds of （Mg₂Si+Si）/Al composites were fabricated by gravity casting method, and their microstructure and wear behaviors were studied. The results show that the Mg₂Si reinforced phase modified by phosphorus exhibits a blocky morphology. When the excess Si increases from 12% to 16%, the number of the primary Mg₂Si and Si increases. The average size of the Mg₂Si decreases with the increase of Si content, while the average size of the latter remains unchanged. Mg₂Si acts as the nucleation substrate of the primary Si. The wear behaviors of the composites with three kinds of silicon content were tested when the grinding disc was 45 steel. The results show that the wear mass loss of the composites decrease with the increase of excess Si from 12% to 16%. When the rotational speed rises from 300 r/min to 1000 r/min, the wear mass loss shows an upward trend. The dominant wear failure mechanism are adhesion wear and abrasive wear.