Abstract: To utilize the resources of daylily flower,the flavonoids in daylily flower was extracted by ultrasonic extraction. The contents of flavonoids were analyzed by high performance liquid chromatography. The antioxidant activity was also studied with DPPH· clearance rate and ·OH clearance rate as indicators. The results showed that the extraction rate was 91.15% under the best extraction condition with ethanol concentration of 75%,ultrasonic power of 198 W and ultrasonic time of 23 min. Catechin,epicatechin,rutin,isoquercetin and naringin were detected in the daylily flowers,among which the content of rutin was the highest. Three different species of daylily flower had good oxidation resistance. The equivalent V_C amount of three species "Dujuan","Jidizhiguang" and "Huofenghua" was 10.88,24.22,17.55 mg/g(dry weight)and 41.97,38.02,35.38 mg/g(dry weight),respectively. This study showed that the daylily flowers were rich in bioactive compounds and had high antioxidant activity.