For EGCG methylation via chemosynthesis, methyl iodide was used as methyl donor and two reaction systems (No.1 and No.2) were designed, in which the molar ratios between EGCG and methyl iodide were set at 1:80 and 1:1, respectively. Reaction products TRI-1 and TRI-2 obtained from reaction system No.1 and No.2, respectively were characterized by HPLCMS and NMR. The results showed that the molecular modification of EGCG could be successfully accomplished by the use of chemosynthesis, and five EGCG derivatives, namely 4″-Me-EGCG, 4′,4″-di-Me-EGCG, 5,3′,4′,5′,3″,4″,5″-hepta- Me- EGCG, 5,7,3′,4′,3″,4″,5″-hepta- Me-EGCG and 5,7,3′,4′,5′,3″,4″,5″-octa- Me-EGCG were identified in the two reaction products, of which, 3 were contained in reaction product TRI-1 and 2 in reaction product TRI-2.