Abstract: The dried seedling of Bin Hao is widely usedas Yin Chen — a cholagogic drug in traditional Chinese medicine. To evaluate the quality of the drug and choose a reasonable collecting season, an HPLC method was developed for the quantitative determination of the 3 main active components (chlorogenic acid, phydroxyacetophenone and scoparone) in Bin Hao.Liquid chromatographie analysis was performed on a Shimadzu liquid chromatograph LC-3A, equipped with a UV spectrophotometric detector SPD-2A, a gradient programmer GRE-3A and a data processor Chromatopac C-E 1 B.Solvent A was distilled water containing 2% glacial acetic acid, and solvent B was methanol containing 2% glacial acetic acid. Elution was started with 85%A+15%B and kept for 15 min, then changed to 60%A+40%B in 5 min and lasted 15 min. Flow rate was 1.0 ml/min. The elution process was controlled with the gradient programmer.The methanol extract of the sample was injected directly to a Zorbax ODS(7μm) column (25 cm×4 mm id), the 3 components we ell separated. Linear calibration curves of the 3 components were obtained and external method was used in the determination.Samples collected from the suburb of Beijing at different growing seasons and from different parts of the plant were analyzed The results were given.The method is accurate, sensitive and simple.