Abstract: In the paper, the high toughness matrix Ti₃SiC₂ was in-situ formed by the joint process of slurry infiltration and liquid silicon infiltration, and Ti₃SiC₂ modified C/C-SiC composites were obtained. The effect of introduction of TiC particle on the infiltration of molten silicon were studied, and the microstructure and mechanical properties of C/C-SiC-Ti₃SiC₂ composites were analysed. The results show Ti₃SiC₂ can be formed by the reaction of TiC with liquid silicon during liquid silicon infiltration, and the existence of carbon is beneficial to the formation of Ti₃SiC₂. The infiltration depth of molten silicon in the micropore (mean size 22.3 μm) can reach to 10.8 cm in one minute. The in-situ formed Ti₃SiC₂ replaces the residue silicon and improves both the flexural strength and the fracture toughness of C/C-SiC-Ti₃SiC₂ composites, which reach to 203 MPa and 8.8 MPa·m^1/2, respectively. For C/C-SiC-Ti₃SiC₂ composites with the depth of 20 mm, the materials with different infiltration depths displays similar phase composition, density and mechanical properties, and no obvious microstructure gradient exist, which indicate the joint process of slurry infiltration and liquid silicon infiltration can be used to fabricate the thick-wall components.