Abstract: In this paper,the effect of the foaming property of soybean protein isolated was improved by using the alkali protease to hydrolysis protein. And several influencing factors were discussed in this paper,such as reaction time,temperature,substrate concentration,enzyme dosage,and p H value. Then by the orthogonal design method the optimal conditions of alkali protease hydrolysis soybean protein isolated to improve foaming property was:time 40 min,temperature 50 ℃,substrate concentration 8%,enzyme dosage 0.04%(w/v),p H8.The optimal hydrolysis conditions to improve the foaming stability was:time 30 min,temperature 40 ℃,substrate concentration 12%,enzyme dosage 0.04%(w/v),p H9. The foaming capacity(217.50%) and foaming stability(93.10%) of modified soybean protein isolated was improved in this study. The foaming capacity and the stability was increased by 61.11% and 20.38% respectively than the raw material of soybean protein.