[Objective] The aim was to purify Horseshoe fern flavonoids and study its antioxidant activity.[Method] Flavonoids were extracted from Horseshoe fern under the conditions of ethanol concentration 70%,material/liquid 1∶40,ultrasonic power 140 W and extracting time 1 h.The optimal isolation and purification technology of Horseshoe fern flavonoids was studied by taking adsorption capacity and desorption rate as indexes.Furthermore,the antioxidant activity of orseshoe fern flavonoids was studied by deter mining...