In order to improve the flow ability and early-stage strength of colloidal alumina bonded corundum castables, the colloidal alumina with 20% of solid content was used as the binder, and tabular corundum aggregates and fines, and active alumina micropowder CL370 as the main starting materials. Influences of setting accelerating agents (magnesia fines and sodium meta-aluminate) on the linear change rate, the modulus of rupture and the microstructure of corundum castables after different heat-treatments were researched. The results show (1) cement bonded corundum castables have the highest modulus of rupture after 24 h of demolding, and colloidal alumina bonded corundum castables have the lowest one; both magnesia fines and sodium meta-aluminate can improve the strength after 24 h of demolding; (2) after firing at 1 000 ℃ for 3 h, the modulus of rupture of all specimens decreases, even lower than that after 24 h of demolding; (3) after firing at 1 600 ℃ for 3 h, the castable specimen added with 0.1 mass % magnesia fines has the highest modulus of rupture; the tabular phases appear interwovenly in the specimen; (4) taking the comprehensive properties into account, 0.1 mass % of magnesia fines is appropriate, and the addition of sodium meta-aluminate shall be lower than 0.3%.