The composition, microstructures and properties of SiC /Al-2O-3/Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO-2 and SiC were investigated. The composition of the composites was measured by X-ray diffraction (XRD). The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed.The experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers“SiC grains“.The denser the SiC/Al-2O-3/Al-Si composites,the higher their bending strength.As the filler “SiC grains” become fine,the bending strength of the composites increases. The composition, microstructures and properties of SiC / Al-2O-3 / Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO-2 and SiC were investigated. The composition of the composites was measured by X-ray The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed. experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers “SiC grains”. The denser the SiC / Al-2O-3 / Al-Si composites, the higher their bending strength. strength of the composites increases.