15%SiCp/2009Al composites bars with various sizes of SiC particles (3.5, 5.0, 10.0 and 15.0 μm) were fabricated via elemental powder metallurgical and extrusion processing. The effects of SiC particles size on mechanical properties of the composites were studied by optical microscopy (OM), scanning electronic microscopy (SEM), transmission electron microscope (TEM) and universal testing machine. The results indicated that SiC particles sizes had great influence on the strength and toughness of composites. With the increase of SiC particles from 3.5 to 15.0 μm, the strength of the composites decreased gradually, while the elongation increased. The composite reinforced with 5.0 μm SiC particles had the best strength and plasticity. The tensile strength (Rm), yield strength (Rp0.2), elongation (A), and fracture toughness (KIC) were 582, 382 MPa, 10%, and 33.7 MPa•m1/2, individually. When the size of SiC particles was 3.5 μm, the breakage was due to tearing of matrix near SiC particles. When the size of SiC particles was more than 5.0 μm, the failure of composite resulted from tearing of matrix near SiC particles and crack of SiC particles. However, there were no debonding of SiC-Al interface because of excellent interface bond between SiC and Al. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.