Abstract: The constant voltage method was adopted to prepare the anodic oxidation film layer of SiC particle reinforced aluminum matrix composites, using 18% sulfuric acid solution (mass fraction). The influence of SiC particle size on the anodic oxidation voltage, the current density stability, and the thickness of anodic oxidation film layer for the aluminum matrix composites was investigated. The protective effect of the anodic oxide film layer on the aluminum-based composite materials was verified by salt spray test, and the influence of the anodic oxide film layer on the mechanical properties of the aluminum-based composite materials was examined by tensile test. The results indicate that the finer particles lead to higher oxidation voltage, better current density stability, thicker coatings, and more uniform and compact microstructures. Anodic oxidation film layer with thicknesses exceeding 8 μm can provide grade 10 protection for the aluminum matrix composites. The anodic oxide layer has almost no effect on the tensile properties of the composites, but significantly improves the surface hardness of the composites.