Resveratrol (RES) is a kind of stilbene compound with bioactivities, and its structure would be destroyed under ultraviolet or heating treatment, thus weakening its bioactivities. Pectin was able to form non-covalent bonds with RES, which was in favor of protecting antioxidant activity of RES. In this study, the structure of pectin was modified by the method of enzymolysis combined with ultrasound treatment. The molecular and microscopic structure of modified pectin was first characterized, and then the interaction mechanism between pectin and RES was discussed by isothermal titration method. At last, the antioxidant activity of RES-pectin complex under ultraviolet or heating treatment was tested. The resulted showed enzymolysis combined with ultrasound modification method remarkably reduced molecular weight and degree of methyl esterification (DM) of pectin. The molecular weight of 4 -min enzymolysis pectin (PE45U) was only 2% of that of unmodified pectin. SEM images showed more irregular fragments of pectin structure after modification. The combined enzymolysis with ultrasound method exposed a great number of –OH of pectin, which considerably increased the interaction sites and affinity between RES and pectin. The interaction sites number between PE45U and RES was 24 times of that between unmodified pectin and RES. The antioxidant activity of RES was significantly enhanced after interacting with pectin under ultraviolet or heating treatment (p<0.05). This study provided new insights to solve the problem of poor ultraviolet and thermal stability of RES and other stilbene when applied in food industry.