Soy isoflavones are flavonoids, a type of secondary metabolite formed during the growth of soybeans, and a biologically active substance. The distribution of isoflavones in nature is limited to a very few plants such as the Fabaceae subfamily Papilionae, such as soybeans, Mexican white beans, alfalfa and mung beans. Among them, only alfalfa and soybeans have the highest isoflavone content. Generally, the isoflavone content in alfalfa is 0.5%-3.5%, and the isoflavone content in soybeans is 0.1%-0.5%.