〔Abstract〕 Objective To study the expression and diagnostic value of miR-1183 in plasma exosomes of colorectal tumors. Methods Electron microscopy, flow cytometry, and nanoparticle tracking analysis(NTA) were used to identify exosomes in plasma samples. miR-1183 expression levels in exosomes of 80 colorectal cancer, 70 colorectal adenoma and 70 healthy control samples were determined by qRT-PCR; the correlation between the expression of exosomes miR-1183 and the clinical data was analyzed by statistics. Results Typical characteristics of exosomes were identified by electron microscopy, flow cytometry, and NTA, it could be considered that plasma exosomes were successfully extracted. The expression level of miR-1183 in plasma exosomes of colorectal tumor group was higher than that of control group; compared with adenoma group, its expression level was significantly higher in colorectal cancer group(allP<0.05). The expression of miR-1183 in plasma exosomes of colorectal cancer group was positively correlated with pathological stage, N stage, M stage, and serum carcinoembryonic antigen(CEA) level(allP<0.05). The expression of miR-1183 in plasma exosomes of colorectal adenoma group was correlated with serum CEA level(P<0.05). As a diagnostic marker, the area under the curve(AUC) of plasma exosomes miR-1183 for colorectal cancer, colorectal adenoma, colorectal tumor, and colorectal benign or tumors were 0.885 7, 0.814 5, 0.852 5, and 0.730 4(allP<0.000 1). Conclusion The expression of exosomes miR-1183 is closely related to the formation and progression of colorectal tumors, and its plasma expression may be used as a marker for auxiliary or hierarchical diagnosis of colorectal tumors.