BN-MgAlON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-MgAlON composite powders as raw material and Y2O3 as sintering additive.Based on thermodynamic analysis,the oxidation resistance of BN-MgAlON composites was investigated and the dynamics of oxidation process was also analyzed.The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy.The dynamics of oxidation resistance of the BN-MgAlON composites was investigated via the analysis of the constant temperature oxidation mass gain curves.The results show that the main components of the material are MgAlON,Sialon,BN and CaYAl3O7 at 1 650-1 750 ℃,and the content of CaYAl3O7 decreases as the sintering temperature increases.The BN-MgAlON composites prepared at1 750 ℃is uniform and compact with the balanced distributions of Al,Mg,O,and N.The oxidation process of BNMgAlON composites in air mainly consists of MgAlON,Sialon and BN oxidation.The section after being oxidized at1 000-1 300 ℃involves three layers,namely,the outer layer,the middle layer and the inner layer.The oxidation process follows the parabola model.The apparent activation energy of the oxidation process is 2.13×105 J/mol and the frequency factor is 4.66×106. BN-MgAlON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-MgAlON composite powders as raw material and Y2O3 as sintering additive. Based on thermodynamic analysis, the oxidation resistance of BN-MgAlON composites was investigated and the dynamics of oxidation process was also analyzed. The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy. Dynamics of oxidation resistance of the BN-MgAlON composites was investigated via the analysis of the constant temperature oxidation mass gain curves. The results show that the main components of the material are MgAlON, Sialon, BN and CaYAl3O7 at 1 650-1 750 ° C, and the content of CaYAl3O7 decreases as the sintering temperature increases. The BN-MgAlON composites prepared at1 750 ° C is uniform and compact with the balanced distributions of Al, Mg, O, and N. The oxidation process of BNMgAlON composites in air mainly consists of MgAlON, Sialon and BN oxidation. The section after being oxidized at 1000-1 300 ° C involves three layers, namely, the outer layer, the middle layer and the inner layer. The oxidation process follows the parabola model. The apparent activation energy of the oxidation process is 2.13 × 105 J / mol and the frequency factor is 4.66 × 106.