In　this　study,　a　high-performance　Mg-8Gd-2Y-1Zn-6Li　(wt%)　alloy　having　a　TYS　of　202　+/-　2.6　MPa,　UTS　of　243　+/-　2.1　MPa　and　EL　of　10.7　+/-　2.3%　was　successfully　fabricated　by　casting,　heat　treatment　and　hot　extrusion.　The　effects　of　intermetallic　compounds　on　microstructure　and　mechanical　properties　were　deeply　investigated.　The　results　show　that　the　studied　alloy　consists　of　coarse　deformed　alpha-Mg　grains　with　(0001)　basal　texture,　fine　recrystallized　beta-Li　grains　with　(002)　texture　and　three　Mg3RE　phase　variants,　which　are　bulk　Mg3RE　phase　with　a　size　range　of　10-30　mu　m,　spot　Mg3RE　phase　with　a　size　range　of　1-2　mu　m　and　spherical　Mg3RE　phase　with　a　size　range　of　0.3-1　mu　m,　respectively.　The　spherical　Mg3RE　phase　has　a　strong　dispersion　strengthening　effect,　while　the　bulk　Mg3RE　phase　acts　as　crack　resources　and　deteriorates　the　ductility.　A　novel　island　like　beta(1R)　phase　(FCC,　a　=　0.78　nm)　is　found　for　the　first　time　in　the　Mg-Gd-Li　based　alloys.　It　has　a　coherent　((1)　over　bar　12)beta(1R//)(10　(1)　over　bar0)(alpha)　interface　at　the　broad　facet　and　a　semi-coherent　((1)　over　bar　11)beta(1R)//(11　(2)　over　bar0)alpha　interface　at　the　end　facet.　The　beta(1R)　phase　transforms　from　beta(H)　phase　at　the　semi-coherent　interface　by　atomic　shear　of　RE　and　Mg　atoms.　The　beta(1R)　phase　provides　a　significant　precipitation　strengthening　effect　to　the　studied　alloy,　while　the　dissolution　of　beta(1R　)phase　results　in　the　age-softening　phenomenon.　The　high-performance　of　the　studied　alloy　is　mainly　attributed　to　the　alpha/beta(　)duplex　structure,　three　Mg3RE　phase　variants,　and　beta(1R　)phase.　(C)　2021　Elsevier　B.V.　All　rights　reserved.