Developing and designing carbon-free refractory materials is an effective alternative to MgO–C refractory materials to produce large-scale, high-quality, low-carbon special steels. Therefore, in this work, excessive MgO is introduced into MgAlON to prepare a series of MgO–MgAlON composite refractories. The enhancement mechanism of comprehensive performance is systematically evaluated, where MgO as a reinforcer features intergranular phase strengthening and grain boundary purification effects. Besides, the pore structure of MgO–MgAlON composite refractories is also optimized to regulate the molten slag wetting behavior. The results demonstrated that MgO–MgAlON composite refractories have apparent porosity of 13.86%–15.84 %, bulk density of 2.78–2.97 mg cm−3, and compressive strength of 204.17–253.97 MPa. When 42.8 % MgO is introduced, the sample strength retention ratio after thermal shock measurement and slag corrosion experiments are 64 % and 75 %, respectively. Consequently, a cost-effective and feasible reinforcement strategy for MgO–MgAlON composite refractories is proposed, paving the way for.