Abstract: Based on the previous work dealing with the process conditions of in-situ synthesized TiB2 particles reinforced SiC by pressureless sintering method, the microstructures and the mechanical properties of obtained TiB2/SiC ceramic composites were studied. It was found that the TiB2 particles distribute homogeneously in the SiC matrix with φ(TiB2) ranged from 5% to 20%. The equivalent-area circle diameters of TiB2 particles in ceramic composites with φ(TiB2) of 5% and 20% are 2.6 μm and 3.9 μm, respectively. Moreover, the introduction of TiB2 phases can suppress the growth of the SiC grains during the sintering. The relative density, Vicker's hardness and fracture toughness of obtained TiB2/SiC increase with the increase of the φ(TiB2). For TiB2/SiC composite with φ(TiB2) of 20%, the relative density, Vicker's hardness and fracture toughness are 94.8%, 29.1 GPa, 5.9 MPa·m^1/2, respectively. Under optimized process conditions, the fracture toughness of TiB2/SiC ceramic composite reaches up to 6.3 MPa·m^1/2.