Several Mg-4Al-4La/Ce alloys were developed and their microstructure and mechanical properties were evaluated. The phase compositions of Mg-4Al-4La alloy consist of α-Mg and Al11La3 phases. While two binary Al-RE phases, Al11RE3 and Al2RE (RE=Ce/La), are formed in Mg-4Al-4Ce/La alloy, and Al11Ce3 and Al2Ce are formed in Mg-4Al-4Ce alloy. The optimal tensile properties are obtained in Mg-4Al-4Ce/La alloy, in which the UTS, YS and δ are 250, 149.2 MPa and 12.24% at room temperature, and 157.8, 116 MPa and 27% at 150oC, and 99.1, 118.2 MPa and 23.2% at 250oC, respectively. The mechanics properties of Mg-4Al-4Ce/La alloy are nearly same with commercial AE44. The compression creep is lower than that AJ62 alloy.