Abstract: The objectives of this study were to investigate the reaction of CSL with peptidoglycan and the effect of a lectin CSL on the ultrastructure of the yeast Saccharomyces cerevisiae, the surface area of yeast with CSL was measured.The result showed that the solid phase assay revealed that CSL binding to peptidoglycan was concentration-dependent and inhibited by D-Mannose or Gal NAc.The interaction of CSL with the yeast cell wall leaded to the change of yeast surface area and cell wall.The concentration of Ca ⁽2 +) content of yeast cell had no obvious change with and without CSL. The smooth surface of yeast and the scraggy surface of yeast with CSL were observed by scanning electron microscope.The result would provide the basic data for the mechanism of CSL to promote yeast fermentation.