In the present study, the modi cation effect of Sr+Ce in Mg 2 Si/Al-Si-Cu composites was investigated for controlling both the microstructure and mechanical properties. Furthermore, the hardness and the abrasive resistance after modi cation were also studied. The results show that when the composites were modi ed by 0.40 mass% Ce, the morphology of the primary Mg 2 Si phase changes to a polygonal morphology with a size of 15 μm. However, in those with a 0.40 mass% Ce and 0.05 mass% Sr addition, the morphology changes to an irregular and equiaxed shape, and the size increases to 50 μm. Furthermore, in the 0.40 mass% Ce and 0.10 mass% Sr addition, the primary Mg 2 Si morphology transforms to a rectangular trapezoid, or T shape, with sizes measuring 70 μm. Additionally, in the 1.00 mass% Ce and 0.05 mass% Sr, and the 1.00 mass% Ce and 0.10 mass% Sr addition, the primary Mg 2 Si morphologies become either polygonal or irregular shaped, respectively. The eutectic phases change shows that, with the addition of Ce or Sr, the eutectic phases exist in the form of the binary eutectic of Al+Mg 2 Si or the ternary eutectic of Al+Mg 2 Si+Si. The hardness test illustrates that the hardness of the 1.00 mass% Ce and 0.05 mass% Sr and the 0.40 mass% Ce and 0.05 mass% Sr, modi ed composites are higher than the unmodi ed composites. The abrasive resistance data shows that modi ed composites with the 1.00 mass% Ce and 0.05 mass% Sr are higher than that of the modi ed and unmodi ed composites with a 0.40 mass% Ce and 0.05 mass% Sr. The abrasive resistance agrees with the hardness test results, and this demonstrates that the Sr+Ce addition can change the microstructure and enhance the mechanical properties of the material.