This　study　investigates　the　effects　of　extrusion　ratio　and　temperature　on　the　microstructure　and　mechanical　properties　of　as-extruded　Mg-11.5Gd-4.5Y-(1Nd/1.5Zn)-0.3Zr　(wt　%)　alloys.　After　hot　extrusion　the　studied　alloys　exhibit　a　bimodal　microstructure　consisting　of　fine　dynamic　recrystallized　(DRXed)　grains　with　relatively　random　orientations　and　coarse　un-DRXed　grains　with　strong　basal　texture.　The　increase　of　extrusion　ratio　promotes　the　DRX,　increases　the　volume　fraction　of　Mg5RE　phase,　and　refines　the　DRXed　grains,　whereas　the　increase　of　extrusion　temperature　decreases　the　volume　fraction　of　Mg5RE　phase　and　coarsens　the　DRXed　grains.　The　increase　of　extrusion　temperature　suppresses　the　DRX　of　Mg-11.5Gd-4.5Y-0.3Zr　(GW)　and　Mg-11.5Gd-4.5Y-1Nd-0.3Zr　(GWN)　alloys,　but　it　has　a　limited　effect　on　that　of　Mg-11.5Gd-4.5Y-1.5Zn-0.3Zr　(GWZ)　alloy.　The　increase　of　extrusion　ratio　improves　the　mechanical　properties　of　GWZ　and　GWN　alloys,　while　it　deteriorates　the　mechanical　property　of　GW　alloy.　The　increase　of　extrusion　temperature　leads　to　a　decreased　strength　and　increased　ductility　of　the　studied　alloys.　The　change　of　mechanical　properties　is　a　result　of　the　competition　between　the　＂strengthening　effect＂　of　DRXed　grains　and　the　＂hardening　effect＂　of　un-DRXed　grains　in　the　changing　bimodal　microstructure.　The　Mg5RE　phase　also　contributes　to　the　alloy　strengthening,　but　the　extensive　Mg5RE　precipitates　acting　as　the　crack　resources　are　detrimental　to　the　ductility,　especially　for　the　GWN　alloy.　With　the　optimum　extrusion　condition　(temperature　of　450　degrees　C　and　ratio　of　20:1)　the　GWZ　alloy　exhibits　the　best　mechanical　performance,　which　is　superior　to　that　of　its　competitor　6000　series　aluminum　alloys.