To explore the effects of high-fat-high-carbohydrate diet on the liver and composition of gut microbiota in blunt snout bream,the histology method and meta-analysis of 16S rRNA gene sequencing was conducted in this study.The blunt snout bream hepatocytes appeared to be disordered in orientation,nuclear migration and vacuolization after feeding with high-fat-high-carbohydrate diet for eight weeks.A total of 175 820 quality-filtered sequences and 588 OTUs (operational taxonomic units) from six 16S rRNA libraries were obtained.The most abundant taxa (top 4) of bacteria at phylum level in both the control and experimental group (high-fat-high-carbohydrate diet) were Fusobacteria,Firmicutes,Bacteroidetes and Proteobacteria.Among these bacteria,the relative abundance of Fusobacteria and Proteobacteria were higher,while the relative abundance of Firmicutes and Bacteroidetes were lower in the experimental group than that in control group.At the genus level,the relative abundance of the main microbiome in the two groups was different.The Clostridium,Romboutsia and Macellibacteroides in the experimental group were two,six and two-fold of the control group,respectively,while the Porphyromonadaceae and Aeromonas were lower in the experimental group.Analysis of unique and shared bacterial flora showed that the control and experimental group shared 82 OTUs.Twenty six OTUs were unique in the experimental group and the most abundant phyla of the unique OTUs were Proteobacteria (57.69%),Acidobacteria (11.54%) and Firmicutes (11.54%).Collectively,these results indicated that high-fat-high-carbohydrate diet fed for certain days could induce serious injury in the liver tissue of blunt snout bream,influence the composition of gut microbiota,and cause imbalance of intestinal flora,which would be bad for the health of their host.