Abstract The effect of Al 2O 3 and ZrO 2 addition in chromia-based refractories was investigated. The strength of ZrO 2-bearing chromia refractories was greatly enhanced by 4–8 wt% Al 2O 3 additive. In the range of 0–12 wt% ZrO 2 addition, 6 wt% ZrO 2 was most beneficial to the improvement in thermal shock resistance. Corrosion resistance was compared by exposing to three kinds of coal slag with various CaO contents. As the substitution of ZrO 2 for Cr 2O 3 increased, slag penetration increased, particularly in the case of the slag containing ∼16 wt% CaO. Considering the trade-offs between corrosion resistance, thermal shock resistance and mechanical properties, the optimum phase assemblage of high chromia refractories consists of the large granular Cr 2O 3 grains bonded by annular (Cr, Al) 2O 3 grains and well-distributed fine ZrO 2 grains.