A new eastern blotting technique has been established for the visual detection and quantitative analysis of bioactive compounds, saikosaponins in crude drugs and traditional Chinese medicines (TCM). Crude extracts of Bupleuri radix and TCM containing saikosaponins were applied to a polyethersulphone (PES) membrane and developed by acetonitrile-water mixture. Separated saikosaponin a (SSa), SSc and SSd were visually detected by an eastern blotting technique using a monoclonal antibody (MAb) against SSa. SSa, SSc and SSd of each 62.5 ng were detected clearly. Colored spots on a PES membrane were analyzed and calculated by NIH Imaging software resulting that three saikosaponins can be determined quantitatively between 62.5 ng to 1.0 mg. The concentrations of saikosaponins showed good agreements with those from the newly established ELISA assay. As another example, a method for a ginseng saponin, ginsenoside Re (G-Re) in crude drugs was also developed.