This project is using production technology of combined removal of impurity method that prepares high purity and high yield food-grade rice protein powder, to transform rice starch sugar residue into rice protein, which is a breakthrough of traditional protein extraction technology. The project can solve technological problems of low protein content and low extraction ratio in current technology. It aims at making the most of rice residues after rice starch sugar production by combined technologies of wet milling, Alkaline-solution dispersion, saponification degreasing, enzymatic hydrolysis and so on. Thus it improves the extraction ratio and extraction purity up to minimum 80%, which increases product quality and production efficiency.