This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{circ}C$ and 90 min.