Using sintered corundum as aggregate, white fused corundum powder, fused spinel powder, ultra-fine α-Al2O3, nano calcium carbonate and hydrated alumina as matrix, effects of nano calcium carbonate additions (0.4%, 0.8%, 1.2%, 1.6% and 2.0% in mass, the same hereinafter) on modulus of rupture, thermal shock resistance and slag resistance of corundum-spinel castables after treating at different temperatures were studied. The results show that nano calcium carbonate decomposes at high temperatures and inª²situ forms calcium aluminates, which can significantly increase the CMOR and HMOR of the castables after treating at 800-1 400 ¡æ; adding nano calcium carbonate obviously improves the thermal shock resistance of the castables, and has little influence on the high basicity slag resistance, however, significantly decreases the corrosion and penetration resistance to low basicity slag.