The Mg2Si/Al-Si composites were prepared by direct melt reaction（DMR）.Effects of pouring temperature and cooling rates on microstructure and mechanical properties of the composites were investigated.The results show that Mg2Si particle and primary Si phase in the composites become fine and uniform with pouring at 750℃,and the mechanical properties of the composites are improved.The mechanical properties are greatly deteriorated as a result of the coarseness of Mg2Si particle and primary Si phase in the composites with pouring at an under-lower or over-higher temperature.Meanwhile,with increasing in cooling rates,the mechanical properties of the composites are obviously improved.