Rice residue, a by-product from starch syrup industry, was hydrolyzed by using pancreatin with the objective of obtaining oligopeptide. Based on single factor tests, hydrolysis conditions were optimized by using a response surface methodology (RSM) on the degree of hydrolysis (DH) and investigating the relationship between DH and the molecular weight distributions. The optimum values for pancreatin concentration, substrate concentration, temperature, pH and hydrolysis time were found to be 1.6 g/100 g protein, 1:9 (w:v), 55℃, pH 8.5 and 3.0 h. The products made by spray-drying and decolorization with molecular weight (Mw) below 1 000 in the final peptides was over 95%, and most of the final peptides were dipeptide or tripeptide.