Abstract: C f/SiC composites were fabricated by self heating chemical vapor infiltration, and their mechanical properties and microstructure were investigated. Effects of the densification of the composites and carbon coating thickness on the mechanical properties of the composites were studied. The following observations were made: mechanical properties of the composites increased as the densification increased. When the density was 1 93 g/cm 3, the flexural strength and fracture toughness were 382 2 MPa and 9 2 MPa·m 1/2 respectively. Carbon coating thickness has evident effects on the mechanical properties of the composites. When the carbon coating thickness was 0 35 μm, the flexural strength was 231 9 MPa. When the carbon coating thickness was 0 55 μm, the fracture toughness was 10 4 MPa·m 1/2 .