SiCp/2024 aluminum alloy composite, strengthened with single particle size (50, 25, 15, 10 μm) and mixed particle size (10 μm+25 μm) SiC, was prepared by hot isostatic pressing and hot extrusion, and then was T4 treated. Effect of SiC particle size on microstructure and mechanical properties of the composite was studied. T6 treatment was conducted on the composite having the best performance, and the change of the microstructure and mechanical properties was investigated. The results show that under condition of single particle size, with decreasing particle size, the SiC particles distributed more evenly in the matrix; the tensile strength of the composite increased while the yield strength, elasticity modulus, percentage elongation after fracture and Brinell hardness changed little. Under condition of mixed particle size, the small-size SiC particles gathered aroud the large-size particles, leading to the decrease of structure uniformity. The tensile strength of the mixed particle size composite was between those of the corresponding single particle size composites, and the yield strength was slightly higher than those of the corresponding single particle size composites. The 10 μm size SiCp/2024 aluminum alloy composite had relatively good performance, and after T6 treatment, the tensile strength, yield strength and Brinell hardness were further improved.