Abstract: Metal matrix composite materials (MMCs)were prepared using commercial pure Al as matrix,and China made Al₂O₃, short fiber and English Saffil Al₂O₃ short fiber as reinforcement. Tensile strength of the MMCs was measured. In situ observation of micro-fracture process of the MMCs and fractography of the tensile tested specimens were carried out using SEM from the experimental results, and fracture mechanisms of the MMCs were also discussed.