Objective: To investigate the differences and diversity changes in gut microbiota between children and adolescents with constipation and diarrhea, and healthy individuals, and to explore the correlation between changes in stool consistency and gut microbiota, in order to provide a scientific reference for the research on intestinal microecology among children and adolescents. Methods: From October 2021 to March 2022, a total of 42 children and adolescents with constipation and 37 with diarrhea from a tertiary hospital in Hangzhou City, and 43 healthy individuals from 3 primary and secondary schools were included in this study. Fecal samples of children and adolescents were collected and then stool genomic DNA was extracted for 16S rRNA gene high throughput sequencing, and the sequencing results were analyzed. In the analysis of alpha diversity, the Kruskal-Wallis rank sum test was used to compare the differences between the three groups, and the FDR multiple testing correction was used for pairwise comparisons. In the analysis of beta diversity, the Adonis test was used to compare the overall differences between the three groups, and the ANOSIM test was used for pairwise comparisons. In the LEfSe analysis, the LDA scores obtained through LDA analysis (linear regression analysis). Results: Alpha diversity analysis showed that there were statistically significant differences in the Shannon index (4.01, 3.81, 4.19) and Simpson index (0.05, 0.06, 0.04) between the diarrhea group, constipation group, and healthy group ( H=6.05, 6.35, P <0.1). Further pairwise comparison showed that the Shannon index and Simpson index of the healthy group were higher than those of the constipation group ( P <0.1). Beta diversity analysis showed that the impact of grouping factors on inter group differences was statistically significant ( R 2=0.045, P <0.1). Community composition analysis showed that there were 234 species in total among the three groups, and 36 unique species in the healthy group, 36 species in the diarrhea group, and 48 species in the constipation group. Species difference analysis showed significant differences in species composition at the genus level among the three groups ( H=0.000 05, 0.000 16, 0.000 20, 0.000 21, 0.000 53, 0.001 39, P <0.1), including Lachnospiraceae of Firmicutes phylum, Eubacterium hallii, Veillonellaceae, Qscillospiraceae, Butyricicoccaceae and Staphylococcaceae, respectively. KEGG abundance statistics and COG functional analysis showed that there were no significant differences in gene expression abundance of the same function among the three groups ( P >0.1). Conclusions The different stool consistency of children and adolescents is related to changes in gut microbiota composition. Compared to the healthy group, children with constipation or diarrhea have disrupted gut microbiota balance, with a shift in dominant bacteria and a higher abundance of opportunistic pathogens.