Abstract: Under microwave irradiation and in the presence of pyridine as catalyst, a series of modified rosin-condensed tannins esters were synthesized by O-acylation reaction between condensed tannins and modified rosin chloride. The target products were analyzed and characterized by means of UV, IR, TG-DTA and elemental analysis. In addition, antioxidant activity and surface activity of the esters were determined. The test results showed that modified rosin-condensed tannins estershave better oil-solubility in peanut oil and better antioxidant activity than those of condensed tannins, and that of dehydroabietic acid-condensed tannins ester (DHA-MET) was the best of all. The surface activity was evaluated by surface tension, emulsifying power and foaming ability. The results indicated that sodium salts of the modified rosin-condensed tannins esters, especially sodium salts of thehydrogenated rosin-condensed tannins esters,had the superior surface activity.