Plate-type alumina ceramics are widely applied as the major components in display and semiconductor manufacturing equipment. These materials are mainly produced by a filter casting method. There have been few studies on the dispersion of these slurries. Therefore, various commercial dispersants were compared and evaluated here in an effort to optimize the slurry dispersion, which affects the homogeneity characteristics in the field of alumina manufacturing. In order to optimize the slurry dispersion, three types of water-based dispersants were selected through preliminary experiments and the viscosity, frequency sweep, particle size distribution, and sedimentation height were compared under optimum conditions after optimizing the amounts of these dispersants. The amount of dispersant in each case was optimized for the 5468CF, BYK-194, and BYK-012 dispersants, after which the frequency sweep, particle size distribution, and sedimentation height were compared according to the type of dispersant. The viscosity, frequency sweep and sedimentation height were thus measured, and it was confirmed that BYK-012, 5468CF and BYK-194 all had excellent dispersibility, in that order. As a result, it could be confirmed that the condition under which BYK-012 was added, at 0.9 wt%, led to the best dispersibility. In addition, microstructural changes of sintered body samples according to the type of dispersant used were observed. These observations indicated that the microstructure of BYK-012 at 0.9 wt% with excellent dispersibility led to suppressed grain growth with a finer pore size.