Superlight alloys, including Mg-7Li-3Zn, Mg-7Li-3Al and Mg-7Li-1.5Al-1.5Zn, were prepared using a resistance furnace under the protection of argon atmosphere. The microstructures and phases of the alloys were studied by optical microscopy, scanning electronic microscopy (SEM), X-ray diffraction (XRD). The mechanical properties of these alloys were measured by a tensile tester. The results show that the Zn and Al added in Mg-Li alloy mainly dissolve in α-Mg phase and β-Li phase. However, there still exists a part of the Al and Mg compound such as Mg17Al12 which is mainly distributed discontinuously at α phase boundary while the most of them in the β phase are granular. The as-extruded Mg-7Li-3Al alloy has the maximum tensile strength and yield strength of 239 MPa (34% higher than the as-cast) and 178 MPa (31% higher than the as-cast), respectively, and the maximum elongation reaches to 27% (93% higher than the as-cast).