In order to make corundum castables satisfy more severe service conditions in high temperature industries, colloidal alumina due to the same main component with corundum castables was introduced for a pure binding system. The influence of three dispersants (citric acid, FS10 and urea) on the flow ability of colloidal alumina bonded corundum castables was researched to choose a suitable dispersant for solving the shaping problem. In order to further understand the influence of dispersants on the flow ability and the mechanism, the rheological property and Zeta potential value of the colloidal alumina dispersant system and the matrix-colloidal alumina-urea-water system were tested. The results show the castables added with the urea have the best flow ability, and the appropriate addition of the urea is 0.5%.