Abstract: With the rapid development of immunotherapy, an increasing number of immune checkpoint inhibitors have been used in clinical settings. Immunotherapy provides a new treatment option for patients with advanced colorectal cancer metastasis. Studies have confirmed that patients with metastatic colorectal cancer with dMMR/MSI-H status are more sensitive to immunotherapy and have a more objective and sustained clinical response than their counterparts. Gut microbiome has been proved to play a certain regulatory role in tumor immunotherapy response, and some bacteria can affect the efficacy of immune checkpoint inhibitors through the immune system or metabolic function of the body. With the progress of the study, the gut microbiome is expected to become not only the predictive biomarkers of curative effect of colorectal cancer immunotherapy, but it can also be a key regulatory factor influencing the results of colorectal cancer immunotherapy. For future clinical treatment, the use of immune checkpoint inhibitors may benefit patients with advanced colorectal cancer.