Abstract: The magnesium alloy matrix composite was fabricated by the squeeze cast with the preform made of crystallized aluminum silicate short fibers as the reinforcement and aluminum phosphate as the binder. The interface microstructure and reaction products were investigated by optical microscope，TEM and HREM. It is shown that the thickness of the interface of the metal matrix composite (MMC) is about 100 nm，and there are not only lots of MgO grains and a small quantity of Mg Al₂O₄ and Mg₂Si nano grains，but also a small quantity of MgP₄ nano grains on the interface. The stronger interface binding force and ideal interface structure are formed between the magnesium alloy matrix and the alumina silicate fibers. Compared with the properties of the AZ91D alloy，the tensile strength of the MMC increases by 18% at room-temperature，and the Young‘s modulus increases by 58%.