OBJECTIVE To detect the effect of Chelidonium majus L. extractive Chelerythrine on the cell surface hydrophobicity and adherence of Streptococcus mutans, and to investigate the mechanism of adherence. METHODS The Chelerythrine was doubly diluted to different concentration from 24.4 microg/ml to 781.3 microg/ml. The method of microbial adhesion to hydrophobicity(MATH) was used to measure the cell surface hydrophobicity of Streptococcus mutans; The effect of the Chelerythrine on Streptococcus mutans adhesion to glass surface was also measured. SPSS13.0 software package was used for statistical analysis, and one-way ANOVA was used to compare the difference of means among sample groups. RESULTS The cell surface hydrophobicity of Streptococcus mutans decreased gradually with the descent of each concentration of Chelerythrine. There was significant difference between each experimental group and control group (P<0.01). There was no significant difference among groups of 195.3 microg/ml, 97.7 microg/ml, 48.8 microg/ml and 24.4 microg/ml (P>0.05). The inhibition rate of adherence increased significantly with the increase of the concentration of Chelerythrine. There was highly significant difference between group of 195.3 microg/ml or 390.6 microg/ml and control group, and the same between the two experimental groups and other experimental groups (P<0.01). CONCLUSIONS There is some degree of inhibitory effect of Chelerythrine on the cell surface hydrophobicity and adherence of Streptococcus mutans. Chelerythrine possesses powerful anticariogenic potential.