Abstract: The microstructure and mechanical properties of GW104+xAl（x=0, 0.4, 0.8, 1.2, wt%） magnesium alloys were studied by OM, SEM, XRD and tensile tests. The results show that the microstructure of as cast GW104 alloy is mainly composed of α-Mg, Mg₃Gd and Mg₂₄Y₅ phases. After adding Al element, Al₂Gd phase is generated in the alloy. The grain of GW104+xAl alloy after homogenization is fine, Mg₃Gd phase and Mg₂₄Y₅phase dissolve into the matrix, and Al₂Gd phase still exists in large quantities. The addition of Al element to GW104 alloy can significantly increase the high-temperature strength by generating Al₂Gd phase. The 300 ℃ high-temperature tensile strength of extruded GW104+1.2Al alloy is 182 MPa, which is 20.5% higher than that of GW104 alloy.