It has been well established that S. mutans is the major etiological agent in dental caries, one of the most common oral diseases worldwide. The present study was designed to investigate the effect of Saururus chinensis (S. chinensis) ethanol extracts on the growth, acid production, biofilm formation, adhesion, and insoluble glucan synthesis of S. mutans. The ethanol extracts of S. chinensis showed concentration dependent inhibitory activity against the growth and acid production of S. mutans, and produced significant inhibition at the concentration of 0.025, 0.05, 0.1, 0.2 and 0.4 mg/ml compared to the control group. The extracts markedly inhibited S. mutans adherence to HA treated with saliva, and cell adherence was repressed by more than 80% at the concentration of 0.05 mg/ml and complete inhibition was observed at the concentration of 0.4 mg/ml. On the activity of glucosyltransferase which synthesizes water insoluble glucan form sucrose, ethanol extract of S. chinensis showed more than 10% inhibition over the concentration of 0.025 mg/ml. The synthesis of insoluble glucan was decreased in the presence of 0.025 ${sim}$ 0.4 mg/ml of the ethanol extract of S. chinensis. Our research strongly suggested S. chinensis was a promising natural product for the prevention of dental caries.