The influence of Y on the microstructure, the mechanical property and the corrosion resistance of Mg-9Li-3Al alloy was investigated by optical microscopy, scanning electronic microscopy (SEM), X-ray diffraction (XRD), mechanical properties testing and electrochemical measurement. The results show that the addition of Y can change the microstructure form of the α phase and reduce its volume fraction. Meanwhile, the binary Al2Y phase is mainly distributed inside the β phase and the α phase is formed. The addition of Y can effectively improve the ultimate tensile strength (UTS) and the elongation (EL) of the alloy. Upon 1.6 wt% Y addition, the UTS of the alloy is up to 190 MPa; the maximal EL reaches 19.3% when the content of Y is 2wt%. The corrosion resistances of the alloy are found to decrease upon Y content less than 1.2wt% and then increase upon Y content from 1.2wt% to 2.0wt%.