Ti3SiC2/Al2O3 and Ti3SiC2-TiC/Al2O3 composite ceramics with various Al2O3 fractions were prepared by Ti, Si, Al, TiC and Al2O3 powers via in-situ reaction. Al2O3 contents in raw materials could influence the reaction process of Ti3SiC2 generated. It would lead to react completely when the Al2O3 volume percentage between 50% to 70%, otherwise TiC as an impurity would be found. Finally the Ti3SiC2/Al2O3 composites with 54.4 wt% Ti3SiC2, and Ti3SiC2-TiC/Al2O3 composites with 54.7 wt% Ti3SiC2 and 9.2 wt% TiC were fabricated successfully. There were two types of TiC existed in composites, called intragranular and intergranular particles. The Ti3SiC2-TiC/Al2O3 composite ceramics with 9.2 wt% TiC showed the higher mechanical properties than Ti3SiC2/Al2O3 composite. From the analyzing of microcrack propagation paths, the dispersed TiC particles as reinforcement agents would cause significant crack deflection, improving the flexural strength and fracture toughness up to 492 MPa and 7.8 MPa.m1/2 respectively.