Abstract: Four crystalline components had been isolated from Hypericum attenuatum Chins., which is wild plant in Hulun Buir Meng of Nei Monggol Zizhiqu. On the basis of spectral analysis, hydrolyzed acid, the prepared derivatives, and the pysico-chemical constants crystalline Ⅰ, Ⅱ of components had been identified as hyperin (hyperoside) and quercetin respectively, crystalline Ⅲ identified with chromatograph is chlorogenic acid with a few impurity. The component Ⅳ is a flavonoid compound too, but it is not identified. The average of the contents of flavonoid in the whole herb is 1.67%, but the contents of flavonoids in the different organs as the flower, the fruit, the leaf and the stem are quite different. The content in the leaf is highest, that in the reproductive organs is secondary and that in the stem is lowest. The resources of Hypericum attenuatum Chois., are abundant in nature. The content of flavonoids in Hypericum attenuatum Chois. is higher. Its pharmacological function is extensive. Therefore, it is a kind of medicinal herb worthily for further study.