To investigate the relationship between common tongue coating types and intestinal flora in patients with colon cancer.Methods:A total of 78 cases of colon cancer patients with 4 common tongue coating types admitted to the First Affiliated Hospital of Harbin Medical University from March 2019 to September 2019 were selected as research objects.The biodiversity and species composition of the flora of each group of patients were analyzed by high-throughput 16S rDNA sequencing.Results:Among the patients，there were 18 cases of thin moss，12 cases of thin yellow moss，22 cases of white moss and 26 cases of yellow moss.There were significant differences in intestinal flora diversity among patients with colon cancer with four kinds of tongue coating(all P<0.05).At the level of phylum classification，the five phyla with the highest abundance in each group were Fimicutes，Proteobacteria，Bacteroidetes，Actinobacteria and Verrucomicrobia.At the taxonomic level，the richness of the top 10 genera in each group was mainly concentrated in Enterococcus，Escherichia/Shigella，Streptococcus，Klebsiella，Akkermansia，Lachnospiracea-incertae-sedis，Blautia，Bacteroides，Erysipelotrichaceae-incertae-sedis，Bifidobacterium.Conclusion:There are significant differences in biodiversity and species composition of intestinal flora with different tongue coating in patients with colon cancer，which provides experimental basis for further study on diagnosis and treatment of colon cancer based on tongue image change.