Abstract: After the concept of liquid biopsy was proposed more than a decade ago, it has quickly expanded to the field of circulating tumor cell (CTC). As a novel biomarker, CTC has the advantages of non-invasiveness, sensitivity, and easy operation, which are incomparable with traditional imaging assay and in vivo detection, therefore it has been an increasingly important technology for tumor diagnosis and treatment. In addition to providing genomic analysis, CTC can provide information at the transcriptomic, proteomic, and epigenomic levels. Compared with other liquid biopsy methods, CTC detection can provide more complete tumor genetic information and show detailed traces of tumor development. Immunotherapy has the best prognosis for colorectal cancer with microsatellite instability (MSI). The detection of CTC has great clinical application value for the prognosis evaluation of colorectal cancer, personalized medicine and the formulation of immunotherapy plans. This review article systematically summarized the various methods of capturing CTC, the prognostic factors that affect the efficacy of colorectal cancer immunotherapy, and how to use CTC characterization to formulate treatment. Schemes, dynamic detection of disease progression, prognosis, evaluation of immunotherapy efficacy and precise treatment are also discussed and prospected.