The　microstructures　and　mechanical　properties　of　the　Mg-5Y-xMM　alloys　have　been　investigated,　where　MM　stands　for　the　Ce-rich　misch　metal.　It　was　found　that　the　additions　of　the　MM　led　to　refinement　of　the　microstructures　and　improvement　of　the　mechanical　properties.　The　dynamic　recrystallization　has　occurred　during　hot　extrusion.　As　a　result,　the　mechanical　properties　of　the　alloys　were　greatly　improved　after　hot　extrusion.　It　was　indicated　that　the　specimens　of　the　extruded　alloy　Mg-5Y-3MM　displayed　a　higher　tensile　strength,　and　the　values　of　the　ultimate　tensile　strength　and　yield　tensile　strength　were　260　and　183MPa,　respectively.