Abstract: Objective　To explore the distribution characteristics of gut microbiota in children with attention deficit hyperactivity disorder (ADHD) and its possible role and mechanism in the pathogenesis of ADHD. Methods　Case-control study was used in this study. From January 2019 to June 2019, 17 ADHD children aged 6-12 years were selected, and 17 healthy children of the same age were recruited as controls. Metagenomic sequencing and analysis of fecal microflora were carried out to compare the Alpha diversity of microflora and the relative abundance of species classification (genus and species) between groups. Results　There was no significant difference in Alpha diversity of gut microbiota between ADHD and control groups (P>0.05). At the level of bacteria genus, compared with healthy children, the abundance of Facelibacterium and Veillonellaceae was reduced while the abundance of Odoribacter was increased in ADHD children, and differences were statistically significant (P<0.05). Furthermore, Enterococcus were significantly increased (LDA>2). At the level of bacteria species, the abundance of Faecalibacterium prausnitzii, Lachnospiraceae bacterium and Ruminococcus gnavus was decreased, while the abundance of Bacteroides caccae, Odoribacter splanchnicus, Paraprevotella xylaniphila and Veillonella parvula was increased in ADHD children, and there were significantly differences (P<0.05). Conclusion　The composition of gut microbiota in ADHD children was abnormal.

Key words: 　attention deficit hyperactivity disorder;　gut microbiota;　macrogenomic sequencing;　child