For the purpose of utilizing tannins in the functional foods and crude drudgs, chemical structure of tannins isolated from Korean green tea were determined. Acetone extract from Korean green tea showed inhibition effect against the angiotensin converting enzyme and xanthine oxidase. The acetone extract, on the separation by the use of Sephadex LH-20, MCI-gel CHP-20, resulted in six kinds of purified tannin and all of them are condensed tannins. Purified tannins were identified to be (+)-catechin, (-)-epicatechin-3-O-gallate, (-)-epigallocatechin-3-O-gallate, (+)-gallocatechin, (-)-epigallocatechin, procyanidin B-3-3-0-gal-late by PMR spectrum, IR spectrum and Mass spectrum. The galloyl tannins showed higher inhibition activity against angiotensin converting enzyme and xanthine oxidase than the no-ngalloyl tannins.