By adopting the in vitro simulated fermentation, enzymatic, chemical and auto oxidation of tea polyphenols (contained 78.09% catechins) extracted from green tea are studied respectively. HPLC results of the oxidation products showed that the absorption peaks of all the products can be clearly distinguished, and the retention time also identical to those of black tea, while auto oxidation products have no TFs. The content of TFs and TRs of tea pigment products produced by optimum chemical oxidation is hig...