Mg-Li　alloys　have　been　widely　applied　in　various　engineering　scenarios　due　to　the　ultralight　feature.　One　of　the　key　factors　determining　the　applications　of　Mg-Li　alloys　is　the　strengthening　methods,　which　have　received　much　attention.　In　this　paper,　a　new　Mg-7Li-2.6Al-0.4Si　(all　in　wt.%)　alloy　was　designed　and　produced　to　improve　the　mechanical　performance.　The　simultaneously　outstanding　mechanical　strength　and　ductility　have　been　demonstrated　by　nano　indentation　and　tensile　test,　including　a　yield　strength　of　192　MPa,　tensile　strength　of　250　MPa　and　elongation　of　22　%.　Based　on　the　microstructural　features　characterized　by　optical　microscopy,　scanning　electron　microscopy　and　transmission　electron　microscopy,　the　excellent　mechanical　properties　were　attributed　to　the　precipitates　and　refined　grain　size.　The　fracture　morphology　was　also　uncovered　to　further　explain　the　good　mechanical　performance.　Overall,　this　work　yields　a　new　Mg-7Li-2.6Al-0.4Si　alloy　with　excellent　properties,　which　suggest　its　great　potential　for　various　applications.