Abstract: In order to study impact of acidic component from Coptidis Rhizoma on glucose- lowering effect of berberine in Hep G2 cells,acidic constituents were separated from Coptidis Rhizoma extracts by column chromatography,and cell assay was performed by MTT and Kit methods in high glucose model. From acidic constituents,ferulic acid was separated and identified by chromatography and spectrum methods. It had obvious peak signal in HPLC.Quantitative determination of ferulic and berberine was finished by HPCL- DAD. Their weight ratio in Coptidis Rhizoma extracts was approximately 32 ∶ 1. Cell experiment showed that berberine 36mg·L- 1in combination with ferulic acid 64mg·L- 1could make glucose consumption increase by 29.4% and elevate cell livability up to 69% in Hep G2 cells,compared with same dose of berberine.The result suggested that ferulic acid,had some synergistic effect on improving glucose- lowering effect of berberine and decreasing cytotoxicity of berberine in Hep G2 cells.