Tongue diagnosis, as a unique method of traditional Chinese medicine (TCM), discriminates physiological functions and pathological conditions by observing the changes of the tongue coating.To evaluate the differences of tongue images and tongue coating microbiome between patients with colorectal cancer and healthy people.The tongue diagnostic information acquisition system was used to photograph the tongue images and analyze the thickness of the tongue coatings in patients with colorectal cancer and healthy people. The next-generation sequencing technology was used to determine the V2-V4 hypervariable region of 16S rDNA to investigate the microbial community structure and diversity on the tongue coating.The tongue coatings in patients with colorectal cancer were obvious thickening compared with tongue images in healthy people. The microbial community structure on the tongue coating was different between patients with colorectal cancer and healthy people.Tongue diagnosis may provide important leads towards novel microbiome-related diagnostic tools and tongue coating microbiome may be a novel biomarker for characterizing patient with colorectal cancer.