In order to further improve the strength and the thermal shock resistance of Al2O3-C materials for steel ladle slide gates, the effects of four kinds of alumina micropowders (unimodal activated alumina micropowder 07RAL, unimodal activated alumina micropowder 15RA, bimodal activated alumina micropowder 22RABL, and calcined alumina micropowder 40CA) on the density, the strength and the thermal shock resistance of Al2O3-C materials were studied. The results show that the density, the strength and the thermal shock resistance of Al2O3-C materials can be improved with the introduction of activated alumina micropowders. Among them, the specimen with bimodal activated alumina micropowder shows the best comprehensive performance, especially the hot modulus of rupture. Its actual application results in steel mills show that the average service life of the Al2O3-C slide plates prolongs, and the problems of cast hole reaming, plate oxidation, roughening and cracking during the use of slide plates are obviously improved.