Abstract: AIM　To develop a micellar electrokinetic capillary chromatographic (MECC) method for the separation and determination of silybin, isosilybin, silydianin and silycristin in Legalon capsules, Yiganling tablets and silymarin. METHODS　A buffer solution containing 30 mmol.L^-1 disodium tetraborate, 50 mmol.L^-1 taurodeoxycholic acid sodium salt and 20 mmol.L^-1 β-cyclodextrin (pH 9.2) was found to be the most suitable electrolyte for this separation. The applied voltage was 20 kV and UV detection wavelength was 288 nm. Rutin was used as internal standard. RESULTS　The average recoveries of 99.9% for silycristin, 98.3% for silydianin, 99.0% for silybin and 98.2% for isosilybin were obtained. CONCLUSION　The method is sensitive and accurate for the analysis of diastereoisomers of silybin and isosilybin.