Based on the experimental observation of animal, the effects of the natural medicines Turkish gall and the union fluorine on dental caries prevention are studied. To provide a basis for the natural medicine to be used for the prevention of dental caries, SPF-SD rats infected with Streptococcus mutans were selected. The caries 2000#, with distilled water, infusion Turkish gall, NaF and CHX solution, as well as the Turkish gall+NaF mixture, respectively, were applied to 5 groups of rats by painting their mouth. The collected rat saliva was cultured, the levels of Streptococcus mutans and dental caries score of Keyes were recorded to see the effects of Turkish gall on the rat growth and reproduction of Streptococcus mutans in their mouth and to evaluate the effects of drugs in inhibiting the formation of caries. The results show that (1) Streptococcus mutans level: as compared with the distilled water, there is a decrease to different extents for all strains, but only for NaF and CHX groups there is a significant difference (P<0.05); (2) caries scores of Keyes: the experimental groups of drugs all show some inhibition effects on the formation of dental caries in rats in varying degrees, of which Turkish gall shows good effects on sulcal-surface and smooth-surface caries (P<0.05), but they are all lower than the NaF group; Turkish gall+NaF group has no obvious role in the synergistic inhibition of caries. The natural medicine Turkish gall inhibits rat oral Streptococcus mutans growth and metabolism, which effectively prevents the occurrence of dental caries.