TiN/O′-Sialon ceramics were prepared by pressureless sintering using high titania slag, silicon fume and bauxite chalmette as the starting materials. Phase compositions and microstructure were analyzed by XRD and SEM. The effect of TiO2 content in the staring materials on densification behavior and mechanical properties was studied. The results showed that the sintered samples consisted of O′-Sialon and TiN. O′-Sialon exhibited equiaxied morphology and the particle sizes were about 1-3μm. TiN showed fine granular morphology and most of the particle have lower size than 0.5μm. For the samples sintered at 1500°C using raw materials containing 30wt%TiO2, bulk density, hardness and flexure strength are 3.1g/cm3, 9.2GPa and 169MPa, respectively.