Soybean isoflavone is a sort of secondary metabolite formed during the growth of soybean. It is mainly distributed in the cotyledons and hypocotyls of soybean in the form of glycosides and free aglycones. It has been shown that free soybean isoflavonehas a great many beneficial physiological functions, such as antioxidation, anticancer and cancer suppression, cardiovascular protection, prevention of osteoporosis and female climacteric syndrome. With the advancement of science and technology, soybean isoflavones have been widely applied in various foods. The reported extraction methods of isoflavones from soybean and their advantages and disadvantages were reviewed, and the biotransformation of glycosidic soybean isoflavones to free aglycones was also discussed. It is believed that this will be helpful for the application research of soybean isoflavones.