Objective To explore the expression differences of the quorum sensing molecule AI-2 of streptococcus mutans iso⁃lated from children with different caries experience. Methods Streptococcus mutans isolated from children with different caries experi⁃ence（high caries strain，medium caries strain，and non-cariogenic strain）were used as the experimental subjects. Vibrio harveyi BB170 was used to detect the yield of AI-2 in each group. Real-time quantitative PCR detecting system（RT-qPCR）was used to mea⁃sure the high caries strain’s expression of LuxS and pfs genes at different growth periods，and the relationship between the synthesis of AI-2 and LuxS and pfs genes was analyzed. Results All the strains produced AI-2，the high caries strain had the highest yield. AI-2 expression was found in the high caries strains at different growth stages. The AI-2 of high caries strain had low expression in the lag phase and pre-log phase，and then reached the peak at the post-log phase（19.00 ± 0.90，P＜0.05），which was 19 times higher than that of the negative control，and began to decline in the stable phase. RT-qPCR results showed that LuxS and pfs genes of high caries strains had the highest expression in the post-log phase，which were 10.47 ± 0.35 and 7.22 ± 0.06 respectively; The transcriptional level of LuxS and pfs genes were consistent with that of AI-2，but the correlation with LuxS was higher（P<0.05）. Conclusion Streptococ⁃cus mutans isolated from children with higher caries experience produced more signal molecule AI-2; and the correlation between AI-2 activity and LuxS gene transcription level was higher than that of pfs gene transcription level.