HPLC and LC-MS/MS were used to establish a comprehensive HPLC analytical method of Yinqiao decoction and identify the chemical constituents of the whole and individual herbs of Yinqiao decoction. YWG-C18 (250 mm x4. 6 mm ID, 10 microm) column was used; the mobile phase was composed of acetonitrile (A) and water ( B, with 3% acetic acid) with gradient elution; the flow rate was 1. 0 mL x min(-1) and the column temperature was set up at 25 degrees C. The detection wavelength was 280 nm. The chromatographic fingerprints of Yinqiao Decoction showed 30 main peaks. Peak 2, 14, 15, 17 were from Lonicera japonica Thunb, peak 3, 12, 13, 24 were from Fosythia suspense (Thunb) Vahl, peak 19, 25, 26, 27 were from Arctium lappa L. , peak 5, 6, 8, 9, 10, 11, 18, 28 were from Glycyrrhiza uralensis Fisch, peak 20, 21 were from Mentha haplocalyx Briq. , peak 22, 23 were from Schizonepeta tenuifolia Briq. , peak 1 presented in the chromatograms of Lonicera japonica Thunb, Fosythia suspense (Thunb) Vahl, Mentha haplocalyx Briq. , Schizonepeta tenuifolia Briq. and Platycodon grandiflorum (Jacq. ) A. DC. , peak 7 presented in the chromatograms of Fosythia suspense (Thunb) Vahl and Glycine max (L. ) Merr. , peak 16 presented in the chromatograms of Mentha haplocalyx Briq. and Schizonepeta tenuifolia Briq. , peak 29 presented in the chromatograms of the herbs except Mentha haplocalyx Briq. and Platycodon grandiflorum (Jacq. ) A. DC. , peak 30 presented in the chromatograms of the herbs except Platycodon grandiflorum (Jacq. ) A. DC. , peak 4 was not identified, maybe it was a new constituent produced during decoction. By comparison of the standards isolated and MS spectra, 14 peaks were identified as 2 ( chlorogenic acid) , 9 ( liquiritin ) , 10 ( 4'-O-[ beta-D-apiofuranosyl (1--> 2 ) -beta-D-glucopyranosyl] liquiritigenin), 12 (forsythiaside), 13 (rutin), 14 (4,5-O-dicaffeoylquiniic acid), 15 (3, 5-O-dicaffeoylquiniic acid ), 16 ( 4-0- [ beta-D-apiofuranosyl ( 1 -->2 ) -beta-D-glucopyranosyl ] isoliquiritigenin) , 17 ( 3, 4-O-dicaffeoylquiniic acid) , 18 (2'-O-[ beta-D-apiofuranosyl (1 -->2 ) -beta-D-glucopyranosyl] isoliquiritigenin) , 19 (arctiin) , 20 (linarin) , 25 (genistein) , 28 ( isoliquiritigenin) . The method could be used to identify the characteristics of Yinqiao decoction, and it could be used to evaluate the quality and quantity of Yinqiao decoction.