Abstract: Objective:To measure antioxidant activity components in Equisetum hiemale L. by determining the total phenolic acid and flavonoids of different solvent extracts,then comparing the antioxidant activity effects. Methods:70% ethanol ultrasonic extracts from Equisetum hiemale L. were partitioned by petroleum ether,ethyl acetate,n-butanol and water to obtain four extracts respectively. Then UV-spectrophotometry was applied to compare the contents of total flavonoids and phenolic acids. In contrast to Vit. C,differences of the reduction ability and the removing ratio to hydroxyl radical,DPPH·,ABTS⁺· were found to evaluate the antioxidant activities.Results:There were remarkable differences in both chemical components and antioxidants among the extracts. The total flavonoids contents of different extracts of Equisetum hiemale L. were 5.70~61.55 mg/g,and the total phenolic acid contents 4.07~19.10 mg/g. It indicated that ethyl acetate extracts had the highest contents of total flavonoids and phenolic acids,and the strongest antioxidant activities among all the extracts. The values of IC₅₀ based on hydroxyl radical,ABTS⁺· and DPPH· were(0.321±0.0026),(0.213±0.0010) mg/mL,and(0.169±0.0014) mg/mL respectively. Conclusion:After the solvent extraction from each phase,the effective components of Equisetum hiemale L. were separated preliminarily. The relative contents of total flavonoids and phenolic acids and their antioxidant activities in the ethyl acetate extract phase were significantly higher than other extraction fractions. And its antioxidant capacity was dose-effect relationship. The experiment showed that the flavonoids and phenolic acids were closely related to their antioxidant capacity.