Magnesium matrix composite was fabricated by vacuum hot pressing technique utilizingTiNishape memory alloy as reinforcement and AZ31 plate as matrix. The microstructure and mechanical properties of the composites at room temperature and elevated temperature were studied by optical microscope, SEM, EDS, DSC and tensile test. The results show：The interfacial bonding of the composites was good. The Mg element in the matrix and the Ti and Ni elements in the TiNi alloy diffused to form an interdiffusion layer of about 1 μm. The mechanical properties of the composites at elevated temperature were better than those at room temperature. The yield strength, tensile strength and elastic modulus of the composites were increased by 61MPa、41MPa and 6.05GPa respectively at 100℃ than at room temperature. The yield strength, tensile strength and elastic modulus of the composites were increased by 39MPa、72MPaand 12.19GPa respectively at 150℃ than at room temperature.