Preparation method of TEA CATECHIN (-)-Epigallocatechin gallate is an ester formed by α-phenylphenol benzopyran and gallic acid. It has phenolic antioxidant properties. Its molecular structure is in the Chemicalbook structure. The 6 ortho phenolic hydroxyl groups have many properties superior to other catechins. It also has antibacterial, anti-inflammatory, anti-oxidant and anti-mutation effects. It can also be used as a reversal of tumor multidrug resistance and can improve cancer cells' resistance to chemotherapy.