Dispersant was used to avoid the agglomeration of aluminum hydrate precipitate and improve the sinterability of calcined alumina powder. The mean particle size of the aluminum hydrate precipitates was 0.26${mu}{ extrm}{m}$ and 0.44${mu}{ extrm}{m}$ when ball-milled with and without dispersant, respectively. After calcination at 110$0^{circ}C$ for 5 hours, the size of the alumina powder without dispersant increased to 0.84${mu}{ extrm}{m}$, while with dispersant slightly decreased to 0.22${mu}{ extrm}{m}$. The most thermally active alumina powder was obtained from the sample calcined at 110$0^{circ}C$ for 5 hours with the 1% dispersant concentration. Using the calcined alumina powder at the above optimized condition, the specimen showed fired density of 3.94g/㎤, 4-point MOR of 364MPa, and KIC of 3.26MPam1/2 after sintered at 155$0^{circ}C$ for 3 hours.