Abstract: Al2O3-TiCN ceramic (AT) and MgO-Y2O3 doped composite ceramic (ATMY) were fabricated by hot-pressing sintering. The effects of sintering temperature and MgO-Y2O3 additive on the relative density, microstructure and mechanical property of composite ceramics were studied. The results show that the relative density of AT and ATMY was not less than 97.3% at the sintering temperature from 1 400 ℃ to 1 600 ℃. When the sintering temperature was no more than 1 500 ℃, the second phase of TiCN could effectively inhibit grain growth in Al2O3 substrate due to the grain boundary pinning effect, and there was no obvious difference between AT and ATMY of the microstructures and fracture toughness. When the sintering temperature was higher than 1 500 ℃, TiCN phase was unable to inhibit the grain growth of Al2O3, resulting in the microstructure coarsening of AT. The fracture toughness of AT sintered at 1 600 ℃ was 4.5 MPa·m1/2. The doped MgO-Y2O3 additive cooperated with the second phase of TiCN could effectively inhibit the grain growth in Al2O3 substrate. When sintered at 1 600 ℃, the microstructure of ATMY was small and uniform, and the fracture toughness reached as high as 5.1 MPa·m1/2.