Abstract: The objective of this study was to evaluate potential probiotic lactic acid bacteria that could be applied to prevent dental caries. A novel biofilm model was developed to screen the special LAB strains resistant to the formation of S.mutans biofilm. Other properties such as the safety of LAB applied in the oral cavity were also investigated.Weissella koreensis RS4 was isolated from brine of soaking amaranth. This strain could destroy the integrity of biofilm structure completely,which caused the decrement rate of the total area of bacteria in the biofilm was 88.72%.This strain also showed excellent co- aggregation ability with pelagic S.mutans,lower adhesion ability on saliva- coated hydroxyapatite,lower sucrose- dependent adhesion ability on teeth surface and resistant to0.8 mg / m L lysozyme,which provided a safety environment for its application in preventing dental caries.