Abstract: Epigallocatechin gallate ( EGCG) with different degrees of acetylating was used in this study, peak reserving time of HPLC and the activity of total antioxidant activity, hydroxyl free radical scavenging, superoxide anion free radical and DPPH free radical scavenging during gradually substituting processing were investigated. The results showed that the peak reserving time of acetylated EGCG was 14.6 ~ 30.6 min, the number of replacing hydroxyl increased and the peak reserving time was delayed with the increasing of acetic anhydride.Free radical scavenging activity of acetylated EGCG exhibited different laws, the total antioxidant activity and DPPH free radical scavenging activity gradually weakened with the increasing of substitution degree, Superoxide anion free radical scavenging activity increased first and then decreased with the increasing of substitution degree, hydroxyl free radical scavenging activity reduced with the increasing of substitution degree, and converted to generating hydroxyl free radicals activity. This suggested that the antioxidant activity of EGCG decreased as the degree of acetylation increased, thus provided the basis for development of acetylated EGCG products.