A process for isolating tea polyphenol and caffeine from Green Tea Leaves using extraction with water, followed by ultrafiltration with a CA-Ti composite ultrafiltration membrane, adsorption by PA resin and finally elution by a mixed solvent system has been developed. After ultrafiltration with the CA-Ti composite ultrafiltration membrane, a product with a tea polyphenol content of more than 40% was obtained. After adsorption on the resin and elution with mixed solvents, a purified product containing more than 90% of tea polyphenol was obtained. A modified gel polarization model for the ultrafiltration process has been proposed and a new method for selection of eluting agents by application of solubility parameters has been devised and shown to be very effective. (C) 2004 Published by Elsevier Ltd.