Mg2Si/AM60 composites were fabricated by in situ synthesis, and their microstructures and properties were investigated for the composites adding different Si contents. The results indicate that some fine Mg2Si particles of cosh shape and chinese script shape appeared in the microstructure by adding crystal Si, but were changed to irregular bulks when the content of Si is high. The composites with more homogeneous distribution of Mg2Si particles were produced by mechanical stirring. The ultimate tensile strength and hardness of composites were increased with the increase of Si, but the elongation was reduced. The ultimate tensile strength increased by 12 % for 1.0 % Si addition and the hardness increased by 48.6 % for 5 % Si addition