The invention provides a reagent kit for detecting colorectal cancer on the basis of liquid biopsy. The reagent kit comprises staining enhancement solution for enhancing staining effects and specific antibodies with fluorescence staining markers. The specific antibodies include CK20 antibodies, CD45 antibodies and CDX2 antibodies; the staining enhancement solution comprises surfactants with the concentration of 0.001-1 mg/mL. The reagent kit has the advantages that target cells can be effectively enriched, and whether the enriched target cells come from early-stage patients who suffer from the colorectal cancer or not can be confirmed; the tumor detection sensitivity can be improved by means of double-tumor-marker detection, and the detection accuracy further can be guaranteed by means of CEP8 detection; the staining effects can be enhanced by the staining enhancement solution, accordingly, the diversified antibodies with the fluorescence staining markers can be combined with the target cells, the target cells can be stained, the good staining effects can be realized, fluorescence is intensive, and boundaries are clear.