Soybean isoflavone were extracted from defatted soybean meal by ultrasonic wave and compared with heating circumfluence method. The results showed that ultrasonic method had lots of merits such as time-saving,energy-saving and high efficiency. The extraction rate of soybean isoflavone by this method for 30min was higher than that by heating-circumfluence for once, 120min about 46% and was equal to the rate of heating-circumfluence for twice, 240min.