The antibacterial peptide CM4 having potent antifungal activity on inhibitiong the cell wall regeneration of Saccharomyces cerevisiae protoplasts.When the peptide increased,the ratio of the regenerated colonies drop obviously.To study the antifungal mechanism of the antibacterial peptide,fluorescence\|labeled peptide mixted with the protoplast of yeast,then confocal laser scanning microscopy were performed.The results indicated that the peptides interactted with the protoplast membrane and damaged the structure of the membrane,then the permeation of protoplast changed.Finally the protoplasts with the peptide failed to regenerate the cell walls leading to killing the cell.