A high-performance liquid chromatographic method and a capillary electrophoretic method for the determination of potassium 3- O-caffeoyl quinate and 7-hydroxymethyl-8, 8-dimethyl-4,8-dihydro-benz [1,4]thiazine-3,5-dione of Xanthium Strumarium L. were developed. In capillary zone electrophoresis, a buffer solution containing sodium borate and sodium acetate was found to be the most suitable approach to determine the contents of these marker substances within 50 minutes. In high-performance liquid chromatography, a buffer solution containing phosphate and acetonitrile was applied to analyze these marker substances within 60 minutes. The effect of buffers on the determination and validation of these two methods was discussed.