Objective:To establish an effective method for simultaneously determining the concentration of brucine and strychnine in rat plasma by HPLC.Method:The processed rat plasma samples were separated on a Kromasil C18 column.The mobile phase consisted of acetonitrile-0.01 mol.L-1 sodium heptane sulfonate and 0.02 mol.L-1 potassium dihydrogen phosphate

adjusted pH to 2.8 with 10% phosphonic acid（24∶ 76）.The detection wavelength was set at 264 nm.Result:Chromatograms showed endogenous peaks not interfering with the analysis.The calibration curves of brucine and strychnine were both in good linearity within the range of 50-2 000 μg.L-1.The mean extraction recoveries were more than 86% while the precisions were less than 8%.The results of stability experiment meet certain requirements for the biopharmaceutical analysis.Conclusion:The method with good sensitivity and precision is applicable to the pharmacokinetic studies of the main compounds in total alkaloids from seeds of Strychnou nux-vomica.