The invention discloses plasma miRNA markers related to auxiliary diagnosis of colorectal cancer and an application of the marker. The markers may include one or more of miR-103a-3p, miR-127-3p, miR-151a-5p, miR-17-5p, miR-181a-5p, miR-18a-5p and miR-18b-5p. The plasma miRNA markers, as a novel biomarker, have good stability, are minimally-invasive, are easy to obtain and have high sensitivity andspecificity. Development and application of the biomarkers may provide diagnosis and further therapy on various diseases, including tumors, with a new direction; the invention provides the plasma miRNA markers, which have clinical diagnosis potential, for the colorectal cancer targetedly. Researching proves that these miRNAs, as non-invasive markers for diagnosis of the colorectal cancer, has reliability and repeatability.