Flavonoids were extracted from “Miliang Kiwifruit” root under ultrasonic assistance, using ethanol as extraction solvent. The technical conditions were investigated based on single factor and orthogonal tests. The hydroxyl radical-scavenging capacities and the antioxidative activities to oils and fats of the flavonoids extracts were assessed and compared with citric acid and Vc. The results showed that the optimal extracting conditions were obtained as follows：60% ethanol, 1:30 (g: mL) material-to-liquid ratio, 40 min of ultrasonic extracting time and 60 ℃ water-bath of ultrasonic temperature. Under the optimal conditions, extraction rate of total flavonoids was 1.5%. The scavenging capability on ?OH free radical increased with extracts concentration increasing. Furthermore, the antioxidant activity of flavonoids extracts was excellent for oils and fats.