Abstract: Objective To explore the mechanism of virulence regulation in group B streptococcus (BGS) by studying LuxS-re-lated AI-2 quorum-sensing pathway in GBS. Methods luxS gene deletion mutants of GBS (△ lusX) were characterized by reverse transcription (RT)-PCR, colony immunoblot analysis, growth curve measurment, and cAMP determination. Functional analysis of luxS in the deletion mutants was conducted by bioluminescence assay. Results Genetic analysis results showed that the luxS deletion in the mutant 515-△lusX caused upregulation of scpB gene expression. Phenotypic analysis revealed that, in comparison with the wild strain, 515-△lusX mutant grew slowly in CDM media but quickly in THY media. An approximately two-fold decrement in bioluminescence was detected in the luxS deletion mutants as compared with the wild strain. Conclusion This study confirms the importance of LuxS molecule in the AI-2 quorum-sensing pathway in GBS and provides new insights into the virulence regulation mechanism of GBS.