In order to solve the problem of strength and toughness of aluminum matrix composites, TiO2/Al matrix composites were prepared by friction stir processing(FSP). The experiments were carried out by microstructure observation test, tensile test and micro-hardness test to characterize and analyze the strengthening mechanism, microstructure and mechanical properties of composites. The results show that with the introduction of TiO2, the grain has been refined, and the crystalline form of Al is change from continuous dynamic recrystallization(CDRX) of invisible core to the particle-stimulated nucleation mechanism by FSP. The tensile strength and microhardness of the composite are improved. When the addition amount reaches 48%（mass fraction）, the tensile strength is 456 MPa, and the hardness is 130 HV, which increases by 17% and 16%, respectively, compared with that of the unadded particles, and the elongation decreases only by 4%. TiO2 prepared by FSP can effectively improve the mechanical properties and improve the strength and toughness mismatch, which provides theoretical basis and technical reference for the application of new composite materials.