Abstract: Objective：To research the effect of quorum sensing inhibitor furanone C-30 on initial biofilm formation of Streptococcus mutans. Methods：The in vitro synthetic quorum sensing inhibitor furanone C-30 was prepared with BHI medium in which Streptococcus mutans was cultivated into different final concentration of 10μmol/L,100μmol/L. Biofilms were formed after being incubaed at 37℃ for 24 h, followed which the kinetic quantification of biofilm formation was detected by BioFilm Ring Test. Results：The furanone C-30 group with a concentration of 100μmol/L was shown to inhibit the biofilm formation by Streptococcus mutans significantly(P<0.05). The time of magnetic beads immobilized and the value of BFI were both different between the 100μmol/L furanone C-30 group and the control groups. Conclusions：Quorum sensing inhibitor furanone C-30 in the concentration of 100μmol/L can inhibit the biofilm formation of Streptococcus mutans. It may direct a new way for the prevention and therapy of caries.