A novel Mg-based composites (Al63Cu25Fe12)p /AZ91 was prepared by pressure die casting protected by CO2/SF6 condition. The–200mesh quasicrystalline powders were poured into the molten AZ91Mg alloy and then rapidly stirred for 30 min in 720°C. The phases and phase transformation in the process of heat treatment for Al63Cu25Fe12 powder, and the reaction between matrix metal AZ91 and Al63Cu25Fe12 particle has been investigated using Scanning Electron microscopy (SEM) and Energy spectrum diffraction analysis technology（EDAX）. It is shown that i-phase decomposed in process of stir and the Cu atoms diffuse from powders into the matrix and combine with Mg and Al in the matrix, which produces metallic-compound dispersing along the grain boundary. The Mg atoms diffuse into the powders and substitute the Cu atom sites. After heated with solution and ageing, composites of (Al63Cu25Fe12)p /AZ91 is different from magnesium alloy, they need less time to get the ageing hardness peak. The mechanics properties of composites have been improved outstandingly by hot-extruded and treatment of solution and ageing, the tensile strength σb is from 189.54MPa up to 359.38MPa. However, because of their brittleness, the plasticity of composites decreased.