Abstract: Different amounts of AlON have been introduced in calcium hexaaluminate (CA₆) using two approaches, that is, one-step and two-step methods, to improve the slag resistance of CA₆. A one-step method can directly sinter the mixtures combining Al₂O₃, CaCO₃, and Al in flowing nitrogen, in which AlON clusters are always formed because of the poor wettability of Al by Al₂O₃, leading to the high porosity of CA₆/AlON composite. In a two-step method, CA₆ and AlON are prepared separately and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by the one-step method, CA₆ and AlON in composite by the two-step method are more uniformly distributed, and the optimized amount of AlON added is 10wt%. The slag corrosion and penetration test shows that the CA₆/AlON composite using the two-step method exhibits superior slag corrosion protection. The promoted effect of AlON on slag penetration and corrosion resistance is also discussed.