Abstract: In order to research the influence of severe plastic deformation on microstructure and mechanical properties of metal matrix composites, powder mixture of pure Al and oxidized SiC were consolidated into 10 wt% (mass fraction) SiC_P/Al composites at 200℃ by high-pressure torsion(HPT). The Al microstructure and SiC-Al interface of different torsion numbers were studied by TEM. The energy dispersive spectrometer(EDS) was used to analysis the elements diffusion. The mechanical properties of different torsion numbers were studied by universal testing machine. The results show that there are a large number of lattice defect in Al matrix after deformation of different torsion numbers, such as dislocation and non-equilibrium grain boundary. There are two different SiC-Al interface which is the SiC-Al interface with SiO₂ layer and new interface that formes between Al matrix and broken SiC particles. SiC-Al bonding is good and elements mutually diffuse at the interface. The tensile strength of 10 wt% SiC_P/Al is increased significantly and the elongation is greatly improved with the increase of torsion numbers. The analysis shows that a large number of lattice defects and fine grains are produced in the samples after deformation of different torsion numbers. The lattice defects and fine grains enhance the elements diffusion and make the interface bonding better. Lattice defects and better interface are the main reasons that the mechanical properties of 10 wt% SiC_P/Al are greatly improved.