With the shell of Garcinia oblongifolia as the raw material,the extraction process of polyphenols from Garcinia oblongifolia is optimized and their antioxidant activity is investigated,and a quantitative analytical method is established to determine the polyphenol content of Garcinia oblongifolia with tannic acid solution as the standard by Folin-Ciocalteu method and spectrophotometry.The results show that under the conditions of extraction time of 35 min,ultrasonic temperature of 70 ℃,extraction pH of 5,solid-liquid ratio of 1∶65(g/mL)and ultrasonic power of 400 W,the polyphenol extraction yield could be as high as 0.73%.The Garcinia oblongifolia polyphenols show strong scavenging effects on both 1,1-diphenyl-2-picrylhydrazyl radical(DPPH·)and hydroxyl radical(·OH),with the maximum scavenging rates of 84.2%and 82.0%respectively.