Abstract: To explore the optimal ultrasonic-assisted extraction conditions of total flavonoids from the flower of Chionanthus retusa Lindl et Paxt.,and evaluate the antioxidant activity. Based on the single-factor tests,the ultrasonic extraction conditions of total flavonoids from the flower of C. retusa Lindl et Paxt. were optimized by response surface methodology in order to increase the extraction rate of total flavonoids. Meanwhile,the antioxidant activity of total flavonoids was assessed by scavenging assays of hydroxyl,superoxide anion free radicals,DPPH radical and resisting lipid peroxidation. The optimal extraction conditions of total flavonoids were ethanol concentration of 65%,liquid-material ratio of 37 ∶1 m L/g,extraction time of 40 min and extraction temperature of 54 ℃. Under the optimal conditions,the maximum extraction rate of total flavonoids was10.736%. Extracted total flavonoids had strong scavenging capacity on hydroxyl,superoxide anion free radicals and DPPH radical,and strong resisting lipid peroxidation in a dose-dependent manners. Response surface methodology was applicable for the optimization of ultrasonic extraction of total flavonoids from the flower of C. retusa Lindl et Paxt. The total flavonoids from the flower of C. retusa Lindl et Paxt. had strong antioxidant capacity. These investigations will be theoretical reference for further development and utilization of the flower of C. retusa Lindl et Paxt.