The high-temperature digestion process is well applied in china for alumina production from diapore, and digestion is the critical process for alumina plant. The present study attempts to extract alumina from diaspore using a synthetic caustic liquor. The effect of important parameters such as digestion temperature and caustic concentration were investigated and the process conditions were optimized using surface response methodology (RSM) based on central composite design (CCD). The different influence of digestion parameters were compared, and the digestion equilibrium equation for extraction of alumina from diaspore was identified. The model equation developed using RSM software shows good agreement with the experimental data, with a correlation coefficient (R2) ≥0.95. The characterization of sample before and after digestion was determined by X-ray diffraction (XRD).