ObjectiveTo establish a reversed-phase ion-pair chromatography (RP-IPC) method for determination of sinomenine content in Sinomenium acutum. MethodsThe IPC method was established using a column of Eclipse Plus C18 (4.6 mm×250 mm, 5 μm) with a mobile phase of acetonitrile and buffer phosphate (0.03 mol/L potassium dihydrogen phosphate and 0.03 mol/L sodium heptane sulfonic acid,adjusted to pH 4.0 by phosphoric acid)1882．The flow rate was 1.0 ml/min; the detection wavelength was set at 262 nm, and the temperature was at 40℃. ResultsThe linearity was obtained over a concentration range of 0.025-0.5 mg/ml(r=1.000). The low limit of detection was 2.5 μg/ml. The intra-day precisions of low, medium, and high concentrations of sinomenine were 1.54%, 0.70%, and 0.45%, and the inter-day precisions were 1.54%,0.70%, and 0.45%, respectively.The average recovery was 99.9%(RSD＝2.9％, n=6), which met the requirement for analysis. Conclusion The present method is simple, fast, and accurate; it is suitable for determination of sinomenine content in Sinomenium acutum.