The　microstructures　and　mechanical　properties　of　the　Mg-Zn-Er　alloys　have　been　investigated.　The　results　show　that　the　alloying　elements　(Zn/Er)　with　different　ratio　have　a　great　effect　on　the　microstructure　and　mechanical　properties　of　the　magnesium　alloys,　especially　for　the　phase　constitutes.　Furthermore,　the　more　attractive　result　is　that　the　quasicrystalline　phase,　as　the　main　secondary　phase,　precipitates　during　solidification　in　the　alloy　with　addition　of　Zn/Er　ration　of　6.　The　cast　Mg-5Zn-0.83Er　alloy　exhibits　the　ultimate　tensile　strength　and　yield　tensile　strength　are　190MPa　and　80MPa　at　room　temperature,　respectively,　with　an　elongation　of　15%.