Abstract: Objective: To investigate the ultrasonic- assisted extract on total flavonoids from Caragana korshinskii kom and evaluate its in vitro antioxidant activity.Methods: On the basis of single- factor test,the ultrasonic- assisted extraction process parameters including the ratio of ultralonic time( A),material- to- liquid ratio( B),ethanol concentration( C) of total flavonoids from Caragana korshinskii kom were optimized by the Box- Behnken design and response surface method,and the yield of total flavonoids was used as the responsive values.Meanwhile,four kinds of free radical scavenging effect of total flavonoids from Caragana korshinskii kom were determined.Results:The optimum conditions for total flavonoids of Caragana korshinskii kom were as follows: ultrasonic time was43 min,material- to- liquid ratio was 1 ∶ 30 g / m L,and ethanol concentration was 75%. Under these conditions,the yield of total flavonoids could reach 3.743%,and RSD was 0.94%. Result of antioxidation showed that total flavonoids from Caragana korshinskii kom had a certain scavenging effect on DPPH·,hydroxyl free radical(·OH),ABTS+free radical and superoxide free radical( O-2·),so it had good antioxidant activity.Conclusion: The BoxBehnken design and response surface analysis could well optimize the ultrasonic- assisted extraction of total flavonoids from Caragana korshinskii kom and had good predictability. The total flavonoids from Caragana korshinskii kom had antioxidant activity in vitro,so this plant was worth further research and utilization.