The effect of α–amylase on enzymatic OSA corn starch was researched.Through hydrolysis experiments,the results showed that hydrolysis temperature,enzyme dosage and reaction time could increase DE value of enzymatic OSA starch.Through hydrolysis response surface analysis,the results showed:enzyme dosage and hydrolysis temperature,hydrolysis temperature and hydrolysis time interacted significantly;DE value increased significantly higher in high temperature than in low temperature;hydrolysis reaction of α–amylase should react under short time high temperature conditions.The optimum conditions of synthesizing enzymatic OSA corn starch(DE=8.01) was enzyme dosage 115U/g,hydrolysis temperature 95℃,hydrolysis time 49 minutes.