Mg-5Li-3Al-2Zn-xRE　alloys　were　prepared.　The　microstructure　and　mechanical　properties　of　as-cast　and　wrought　specimens　were　studied.　RE　elements　in　Mg-5Li-3Al-2Zn　alloy　cause　the　microstructure　refinement　and　the　formation　of　Al3La,　which　bring　about　the　improvement　of　mechanical　properties　of　alloys.　The　optimal　RE　content　for　Mg-5Li-3Al-2Zn　alloy　is　2　wt%,　which　makes　the　microstructure　the　finest　and　the　mechanical　properties　the　best.　The　further　increase　of　RE　content　makes　the　microstructure　be　coarsened　and　the　morphology　of　Al3La　change　from　particular　to　rod-like　and　pearlite-like　eutectic　shape,　leading　to　the　poor　mechanical　properties　of　alloys.