Mg matrix composites（Al63Cu25Fe12）p/AZ91 with 10%（Al63Cu25Fe12）p in volumetric fraction was successfully prepared by die casting in condition of CO2/SF6 protection,in which the approximately 200 mesh quasi-crystalline Al63Cu25Fe12 powder was poured into the AZ91 molten alloy and then rapidly stirred for 30 min at 720℃.Reaction of quasi-crystalline particle with the matrix alloy was analyzed with the help of SEM（scanning electron microscope）and EDAX（energy spectrum diffraction analysis）,and effects of heat treatment on properties of the composites were evaluated.The results reveal that quasi-crystalline I phase is decomposed during stirring process,and Cu atom free decomposed from quasi-crystalline I phase is diffused into the matrix alloy to react with Al atom in the matrix alloy,and created intermetallic compound is distributed around the quasi-crystalline particle,meanwhile,Mg atom is emerged into the powders to substitute the sites of Cu atoms.Aging peak value of the composites is significantly delayed,exhibiting solution and aging characteristics distinctly different from the matrix alloy.Mechanical properties of the composites after hot extrusion and heat treatment are obviously improved,where tensile strength is increased from 189.54 MPa of as-cast AZ91 alloy to 359.38MPa,however,plasticity is slightly decreased.