Abstract: Equol is the final metabolite of soy isoflavones in the human intestinal gut.Many studies have been shown that the isoflavones have a wide range of nutrition value and play an important role in the prevention of cardiovascular disease, breast and prostate cancer.The biological activities of isoflavones to some extent be attributed to equol, and equol has a higher biological activity than its precursor.Soy isoflavones can be transformed to equol exclusively by intestinal bacteria, and not everyone have this metabolic capacity.This paper overviewed the physiological activity of equol and a chemical synthesis of R-and S-equol, furthermore, about the biosynthesis of equol.We also introduced some intestinal bacteria capable of transforming soy isoflavones to equol.