Abstract: Wet processing was adopted to produce soybean powder, soybean was grinded by the hot solution of 85℃ 0.3% sodium bicarbonate through scalded 85℃ and kept on 4min, the ratio of bean and water was 1:7, then boiling condition was 95℃ and kept it 20min to get rid of lipoxidase and flavor of soybean, at the same time the urease was negative.Papain enzyme was used to hydrolyze soybean protein with single-factor and response surface optimization, the optimum conditions:pH was 7, addition of enzyme was 8765U/g pro, enzymatic temperature was 54℃, enzymatic time was 1.8h.Under the optimum conditions, the NSI value was 85.83%.