Microstructure　and　mechanical　properties　of　the　Mg-13Gd-5Er-1Zn-0.3Zr　alloy　were　investigated　by　optimal　microscope　(OM),　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD),　energy　dispersive　X-ray　spectrometer　(EDS)　and　transmission　electron　microscopy　(TEM)　in　the　present　investigation.　The　results　suggested　that　the　basal　plane　stacking　faults　(SF)　of　Mg　crystal　was　present　together　with　the　precipitation　of　the　(Mg,Zn)(5)(Gd,Er)　phase.　The　parts　of　the　(Mg,Zn)(5)(Gd,　Er)　precipitate　were　dissolved　into　the　matrix　during　homogenization　treatment　at　733　K.　In　addition,　a　new　kind　of　lamellar-shaped　14H　long-period　stacking-ordered　(LPSO)　structure　was　precipitated　from　the　stacking　faults　of　basal　plane　during　homogenization　treatment　at　733　K.　However,　the　unstable　beta＇　phase　was　precipitated　in　the　extruded　grains　after　ageing　treatment.　The　presence　of　both　the　14H-LPSO　structure　and　the　beta＇　precipitate　resulted　in　a　great　enhancement　in　mechanical　properties.　The　values　of　the　tensile　yield　strength　and　ultimate　tensile　strength　were　338.8　MPa　and　410.9　MPa,　respectively.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.