Abstract： Objective To investigate the effect of Streptococcus mutans luxS mutantation on the early biofilm formatien. Methods Based on the immobilization of magnetic beads by adherent cells, an assay of biofilm quantitative analysis was developed for the kinetic quantification of biofilm formation in this study. Streptococcus mutans luxS mutant strain was constructed and subject to this biofilm luxS mutant strain were compared. Results The AluxS mutant started to form a biofilm from the 6 th hour(△BFI=2.015 ), and the △BFI of luxS mutant increased more quickly than that of the wild type strain, until reaching a complete immobilization of the beads after 10 hours(△BFI =7. 025). The wild-type strain start to form a biofilm from the 10 th hour(△BFI = 1. 875) and the beads were completely immobilized between 12 and 14 hours. Conclusions The luxS mutation can accelerate biofilm on a polystyrene surface during the mid-exponential growth phase. And a luxS-dependent signal may play an important role in the early biofilm formation of Streptococcus mutans.