Abstract: Objective：To evaluate the role of curcumin in initial adhesion and aggregation during biofilm formation by Streptococcus mutans（S.mutans）. Methods：The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by dilution method. The bacteria of S.mutans were resuspended to 1×108 CFU/mL in PBS medium after collecting them by centrifugation. The biofilm adhesion assay with different concentrations of curcumin was under the condition of 37 ℃ and the quantification was evaluated by MTT method. The aggregation assay and hydrophobicity assay were also tested. Confocal laser scanning microscope (CLSM) was used to observe the initial biofilm formation morphology. Results：The MIC and MBC of curcumin on S.mutanswere 32 mg/mL and 128 mg/mL respectively. The biofilm adhesion quantification,aggregation andhydrophobicity of S.mutanswith different concentrations of curcumin were decreased. The images showed by CLSM that the initial biofilm appeared more diffuse and looser with large gapswith different concentrations of curcumin. Conclusions：Curcumin can affect the initial adherion and aggregation during biofilm formation by S. mutans.