In order to further develop and utilize the rutin from Sophora japonica, the contents of total phenolic acids and flavonoids in rutin extracts from different parts of Sophora flavescens were determined, and their antioxidant activities were compared, and the basis of antioxidative activity of Sophora flavescens nanometers was discussed. The experiment found that the total flavonoid content of each extract of Huai Mi was in the range of 5.70–61.55 mg/g, the total phenolic acid content was in the range of 4.07–19.10 mg/g, and the total flavonoid and phenolic acid content of the ethyl acetate extract was significantly higher than other extracts. Its reducing power, light free radicals, DPPH, ABTS+, and scavenging rate are also significantly higher than n-butanol, petroleum ether, and aqueous extracts. ∗The cleaning ability IC50 values of DPPH· are (0.321 ± 0.0026), (0.213 ± 0.0010), and (0.169 ± 0.0014) mg/mL. The effective components of Sophora japonica are initially separated after the solvent extraction of each phase. The relative content and nanoantioxidant activity of total flavonoids and phenolic acids in the ethyl acetate phase extraction part were significantly stronger than those in the total extract and other extraction parts, and the antioxidant capacity was effectively related to the dose. The flavonoids and phenolic acids in Sophora japonica are closely related to its antioxidant capacity.