The　tensile　and　tensile　creep　properties　of　the　as-cast　Mg-5Zn-2.5Er　(in　wt.%)　alloy　strengthened　by　icosahedral　quasicrystalline　phase　(1-phase)　were　studied.　The　Mg-5Zn-2.5Er　alloy　had　better　tensile　properties　both　at　room　temperature　and　175　degrees　C　than　AE42　and　Mg-5Zn　alloys.　Compared　to　AE42　alloy,　the　as-cast　Mg-5Zn-2.5Er　alloy　had　smaller　steady-state　creep　rate　and　total　creep　strain　under　the　creep　conditions　of　175　degrees　C　and　70　MPa　for　100　h.　The　better　creep　resistance　of　the　Mg-5Zn-2.5Er　was　mainly　due　to　the　formation　of　I-phase　with　high-thermal　stability　distributed　along　grain　boundary.　Moreover,　microstructure　analysis　indicated　that　some　fine　precipitates　in　the　alpha-Mg　matrix　can　pin　the　dislocation　effectively,　improving　the　creep　resistance　of　the　alloy.　(C)　2009　Elsevier　B.V.　All　rights　reserved.