The technique of hydrolysis of soybean isoflavones by saccharifying enzyme was studied in this paper.The soybean isoflavone aglycon was obtained by hydrolysis.The different factors influencing the process of enzyme hydrolysis were studied through single factor tests.Reaction conditions of hydrolysis by saccharifying enzyme were optimized through orthogonal test.The results showed that the optimal hydrolysis conditions were as follows: the temperature was 55℃,the pH value was 4.8 and the time was 7 hours.The hydrolysis ratio could reach 98.18%.