Objective:Quorum sensing regulates the formation of Candida albicans (C. albicans) biofilm. Farnesol and tyrosol are quorum sensing molecules produced by C. albicans. The aim of this study is to find the effects of quorum sensing molecules on the formation of C. albicans and biofilm in different time phases of biofilm. Methods:C. albicans biofilm was constructed in vitro. The study C. albicans biofilm were separated into the tyrosol treated group,the arnesol treated group,the tyrosol and farnesol co-treated group and the no-treated control group. The effects of the tyrosol and farnesol on C. albicans cell viability in different time phases were detected by XTT method. The effects of the tyrosol and farnesol on C. albicans biofilm formation were observed by scan electronic microscope (SEM). The production of farnesol and tyrosol of biofilms was detected by gas chromatography-mass spectrometry (GC/MS) and high press liquid chromograph (HPLC),respectively. Results:The XTT method suggested that biolfilm activitity was promoted by tyrosol at 6 h (P < 0.05),while it was suppressed by farnesol at 3 h and 6 h (P < 0.05). Biofilm activity of the tyrosol and farnesol co-treated group was inhibited at 6 h (P < 0.001). The SEM observations showed that tyrosol contributed to the germ tube formation of the C. albicans biofilm at 3 h and 6 h. Farnesol inhibited the hyphae growth of biofilm at 3 h and 6 h. The tyrosol and farnesol co-treated group showed that the effect of tyrosol was not antagonistic to that of farnesol. GC/MS and HPLC results showed that C. albicans produced little tyrosol and farnesol at early stage and showed no obvious rising trend (P > 0.05). With biofilm maturation (24 h and 36 h),the production of tyrosol increased significantly (P < 0.05),which of farnesol was also increased significantly (P < 0.05). In all,C. albicans produced most tyrosol at 24 h and most farnesol at 36 h. Conclusion:Tyrosol contributed to the biofilm formation by increasing the germ tube formation of the C. albicans biofilm. Farnesol inhibited the C.albicans biofilm formation by decreasing the germ tube formation. The inhibition of farnesol to the hyphae growth was more powerful than the contribution of tyrosol to the germ tube growth in the co-treated studies.