is a traditional medicinal plant popularly used in China. This study intended to evaluate the antioxidant properties and the chemical components of the flavonoid-rich extracts from the flowers of . The results showed that the flavonoid-rich extracts from the flowers of had strong scavenging capacities on 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), hydroxyls, superoxide anions, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in a dose-dependent manner. Five flavonoids, dihydrokaempferol ( ), apigenin-7- -β-d-glucoside ( ), apigenin-7- -β-d-neohesperidoside ( ), kaempferol-7- -β-d-glucopyranoside ( ), and kaempferol-3- -β-d-glucopyranosyl-7- -β-d-glucopyranoside ( ), were isolated from the flavonoid-rich extracts of the flowers of . High-performance liquid chromatography (HPLC) analysis revealed that compounds and were abundant in the flower and in flavonoid-rich extracts. The main components of the flower of are flavonoids. The high antioxidant activity of the flavonoid-rich extracts may be attributed to the high content of flavonoids. The five isolated flavonoids were the primary antioxidant ingredients, and may play important roles in the strong antioxidant activities of this flower. Based on the obtained results, the flower of could be a potential source of natural antioxidants in food and pharmaceutical applications.