Abstract: The extracted mixture of the root of Lespedeza formosa from purified water, 95% ethanol and petroleum ether were studied by test-tube, chromogenic and paper reaction. Rutin as a reference substance and aluminum trichloride as chromogenic agent, the content of the total flavonoids were determined by UV-Vis spectrophotometry. The preliminary test indicated that the root of Lespedeza formosa contained flavonoids, saccharides, polysaccharides, glycosides, organic acids, phenols, tannins and anthraquinones. The well linear ranges of rutin were 0.004~0.040 mg/mL（r=0.999 6） and the regression equation was Y=35.142 2X+0.040 645 3. The average percentage of recovery was 95.29%, the RSD was 0.65%. The total flavonoids content of 10 batches in root of Lespedeza formosa were 31.84~75.85 mg/g. The chemical components in the root of Lespedeza formosa were determined. The method of determination of the total flavonoids is stable and reliable. It provides experimental reference for developing and utilizing the root of Lespedeza formosa.

Key words: the root of Lespedeza formosa, chemical constituents, UV-Vis spectrophotometry, total flavonoids