Abstract: Recent research has shown that gut microbiome is closely related to tumorigenesis. Our body is exposed to a large number of intestinal microbiome and its metabolites, which constitute the ecological environment of the organism. Gut microbiome is involved in the occurrence and development of cancer through several diverse mechanisms. Immune checkpoint inhibitors have recently made breakthroughs in treating various malignant tumors, and increasing evidence suggests that intestinal microbiome has an important effect on tumor immunotherapy, especially immune checkpoint inhibitors. This review focuses on the role and effect of gut microbiota on tumor immunotherapy in recent years to provide a reference for the application of immune checkpoint inhibitors in tumor therapy.