The as-cast Mg-6Y-3Zn-xLi （x=0，5，8 and 11wt%） alloys were prepared by vacuum induction melting under controlled argon atmosphere.The alloys were then processed by homogenized treatment and hot extrusion. The effects of Li content on the microstructure and mechanical properties of the alloys were investigated by using OM， SEM and tensile test. The results showed that， with increasing Li content， the as-cast Mg-6Y-3Zn-xLi alloys were transformed gradually from single α phase structure to （α+β） dual-phase structure. Meanwhile， the grain size of Mg matrix， morphology and distribution of eutectic compounds were changed remarkably. After homogenized treatment， block-like long-period stack ordered （LPSO） phases formed in the Mg-6Y-3Zn-xLi alloys. As Li content increased， the volume fraction of LPSO phases decreased， while the amount of （Mg，Zn）₂₄Y₅ phases increased. Tensile test results indicated that as-extruded Mg-6Y-3Zn-8Li alloy exhibitsed the best comprehensive mechanical properties，i.e.，the ultimate tensile strength and elongation reached to 278 MPa and 11.6%， respectively.The improvement of mechanical properties was mainly attributed to the complex strengthening mechanism by the distributed fragmented and refined LPSO phases and the great amount of fine dynamic recrystallized grains.