Abstract: Alcalase was utilized to purify rice starch prepared by dilute alkali, the conditions of enzymatic hydrolysis were pH 9, 45℃, the ratio of enzyme to protein 48 AU/kg and 60 min. The content of protein in rice starch was decreased from 2.87% to 0.4%. The analysis results of scanning electromicroscope showed that protein granules didn't obviously exist in rice starch pured by alcalase, and the solubility and swelling power of rice starch increased remarkably after purification.