The mechanical properties of SiC Particulate reinforced AZ81 magnesium Base composites prepared by powder metallurgy were studied in the article. The mechanism of mechanical properties was also investigated. The experimental results show that tensile strength, fracture toughness, Vickers hardness of SiCp/AZ81 composites were remarkably improved when a proper volume of SiC were added, their maximum can reach 271.61 MPa, 5.96 MPa-m1/2, 2.52 GPa, respectively.