Abstract: Capillary electrophoresis and amperometric detection (CE-AD) was applied to the separation and simultaneous determination of clonidine hydrochloride,hydrochlorothiazide and rutin,3 active ingredients of the ready-prepared Chinese medicine “Zhen Ju” hypertension pills.In a buffer medium of 25 mmol·L-1 Na2B4O7 and 50 mmol·L-1 NaH2PO4 with its original pH value of 7.9,three electroactive substances mentioned above were separated completely within 15 min.The large differences in concentrations of the 3 compounds (0.03,5 and 20 mg per pill respectively) in the hypertension pills made it difficult to the simultaneous determination.The difficulty was overcome by choosing water as a diluent for the sample solution,thus making a reasonable adjustment of the current responses of the 3 ingredients at the carbon electrode,and the simultaneous determination was made possible,giving values of relative deviation less than 2%,from the labelled values of each pill.