Abstract: The diversity of fermentation pit mud(FPM)reflects the FPM quality and determines the quality of Chinese strong-flavor liquor. In this study,bacterial diversity in degenerated and normal(n=5)pit mud samples(n=5)was profiled by Miseq high-throughput sequencing of the 16S ribosomal RNA gene. The results indicated that Chao1 index and Shannon index were significantly higher in degenerated pit mud than that in normal ones(p<0.05). Clostridium,Syntrophaceticus,Syntrophomonas,Petrimonas,Sedimentibacter,Aminobacterium,Lysinibacillus,and Pelotomaculum were found to be significantly higher in degenerated pit mud(p<0.05),whereas Lactobacillus,Bacillus,Ralstonia,and Nocardia significantly higher in normal pit mud(p<0.05). Both principal coordinate analysis and clustering analysis based on weighted unifrac distance showed structural segregation between the two group samples. Nine operational taxonomic units(OTUs)were identified by redundancy analysis as key variables significantly associated with the structural difference. Four OTU closely related to Lactobacillus were enriched in the bacterial microbiota of normal pit mud,whereas 5 OTUs related to Clostridium,Syntrophomonas,Pelotomaculum,and Synergistaceae. This study might help clarify the relationships between microbial community and pit mud quality.