The influence of ethanol concentration, solid-liquid ratio, amount of ammonium sulfate, microwave power and microwave radiation time, on the yield of flavonoids, was investigated by microwave-assisted aqueous two-phase method. The experimental model, in which flavonoids were extracted, was established by Box-Behnken experimental design. The results showed that when the ethanol volume fraction was 60%, the solid-liquid ratio was 1∶40 (g/mL), the amount of the ammonium sulfate was 4 g, the microwave radiation time was 90 s, and the microwave power was 270 W, the yield of the flavonoid was 20.74%, which relative error was 0.97% for the model calculated value 20.94%. The product had good doze-effect relationship for DPPH·, and the scavenging ability was stronger than V_C and rutin in 1.5 μg/mL.