Abstract: Mg-xGd-3Y-(1Zn)-0.5Zr alloys were prepared by high flux vacuum melting furnace. Optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), field emission trams mission electron microscope (TEM) and MTS hydraulic servo testing machine were used to study the effects of different Gd contents on the microstructure and mechanical properties of the as-cast alloys. The results show that the microstructure of the as-cast alloys is composed of α-Mg matrix, Mg₅(Gd, Y) phase and lamellar 18R-LPSO phase. With the increase of Gd content, the volume fraction of Mg₅(Gd, Y) phase and LPSO phase gradually increase, the grain size shows a trend of refinement, and the tensile strength gradually increases. The as-cast alloy with the Gd content of 10wt% has the best tensile properties, and its tensile strength and yield strength at room temperature are 271 MPa and 196 MPa, respectively.