Tea polyphenols is natural compound extracted from tea. It is composed of more than 30 substance containing phenolic group, its chemical structure can be sorted four types: catechin type, flavone and flavonol type, anthocyanidin and procrypsis anthocyanidin type, phenolic acid type; among of them, type catechin is the most occupying 60%~80% of total phenols. Catechin type is composed of D,L-C, EC, EGC, EGCE, GCG, ECG and so on, the first three types are the simple catechin ( free type), the latter three types are the complex catechin (ester type). Catechin compound is apt to show oxidation, polymerization and condensation for containing more phenolic hydroxyl group, which is doomed to have fine ability of anti-oxidation and ability of clearing free radical.