The　microstructures　of　as-cast　and　as-solution　Mg-12Gd-2Er-1Zn-0.6Zr　alloys　were　investigated　by　optical　microscopy　(OM),　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　high-resolution　transmission　electron　microscopy　(HRTEM),　X-ray　diffraction　(XRD)　and　selected-area　electron　diffraction　(SAED)　in　the　present　investigation.　The　results　show　that　the　primary　eutectic　phase　Mg-5(Gd,　Er,　Zn)　and　some　flocculent　features　are　found　in　the　as-cast　alloy;　the　SAED　pattern　indicates　that　these　flocculent　features　are　the　dense　areas　of　stacking　faults.　The　14H-LPSO　structure　precipitates　in　the　temperature　range　of　673-793　K,　and　the　volume　fraction　of　14H-LPSO　structure　increases　with　the　extension　of　heating　time;　however,　there　is　no　precipitation　of　14H-LPSO　structure　when　the　temperature　reaches　up　to　803　K.　In　addition,　the　Mg-5(Gd,　Er,　Zn)　phase　dissolves　gradually　along　with　the　precipitation　of　14H-LPSO　structure.