Magnesium-based　composites　reinforced　with　stable　icosahedral　quasicrystal　particles　have　been　fabricated　via　Repeated　Plastic　Working　(RPW)　process.　The　microstructure　of　the　composites　has　been　investigated　by　XRD,　SEM,　TEM　and　HREM,　and　its　mechanical　properties　have　also　been　studied.　The　results　showed　that　the　RPW　process　could　reduce　the　matrix　grain　size　significantly,　and　the　average　grain　size　of　matrix　was　only　about　500　nm　after　200　cycles　of　RPW.　A　good　metallurgical　bond　interface　between　the　quasicrystal　particles　and　the　Mg　matrix　was　found.　The　composites　exhibited　the　maximum　yield　strength　of　265M　Pa　and　the　maximum　ultimate　tensile　strength　of　309M　Pa　at　room　temperature,　respectively.　The　enhancement　of　mechanical　properties　is　attributed　to　the　strengthening　effect　of　the　quasicrystal　particles　and　the　fine-grain　size　of　matrix.