Abstract: In order to demonstrate the inhibitory effect of polyphenols from Arctium lappa roots (ALP) on lipase, the ALP were extracted and enriched. The content of total polyphenol was determined by Folin-Ciocalteu method, and the index components in ALP were determined by high performance liquid chromatography-UV (HPLC-UV) method. The inhibitory effect and type on lipase of ALP and its index components were determined by p-nitrophenyl butyrate (p-NPB) method. Combined inhibitory effect of them were evaluated by equivalent line diagram method and drug combination index (CI). The results showed that the total polyphenol of ALP reached 51.23%, and the contents of the five index components, i.e., neochlorogenic acid, cryptochlorogenic acid, caffeic acid, chlorogenic acid, and isochlorogenic acid A accounted for 12.87%. ALP showed reversible competitive inhibition on lipase with half maximal inhibitory concentration (IC₅₀) value 1.706 mg/mL. The IC₅₀ of neochlorogenic acid, cryptochlorogenic acid, caffeic acid, chlorogenic acid, and isochlorogenic acid A were 0.872, 0.910, 0.280, 0.847, 0.244 mg/mL, respectively. When the concentration ratio of chlorogenic acid and isochlorogenic acid A was 1:2.15, the CI value was 0.549, and when the concentration ratio of caffeic acid to isochlorogenic acid A was 1:0.87, the CI value was 0.282, which indicated synergistic inhibition effect on lipase. This study provides a theoretical basis for exploring the chemical basis of the lipid-lowering effect of Arctium lappa roots and its lipid-lowering mechanism, and layed a foundation for the development of Arctium lappa roots.