Objective: To study the diagnostic value of colonoscopic narrow-band imaging (NBI) for colon polypoid lesions with the diameter <2 cm. Methods: A total of 86 patients with the colon polypoid lesions diagnosed in our hospital during February 2018 to February 2019 were enrolled. Routine enteroscopy and colonoscopic NBI were performed in the patients, and the morphology of colonpolypoid lesions including the overall lesion, glandular opening type and capillary were observed, and the images were assessed with clarity score. Biopsy specimens obtained during performing colonoscopy were analyzed by pathological examination, and the diagnostic efficacy of NBI were assessed by comparing the results of pathological examination. Results: A total of 104 colon polypoid lesions were detected among 86 patients, and the diameters of lesions were 0.1-2.0 cm and the average value was（0.72±0.34） cm. The NBI International Colorectal Endoscopic(NICE) classification of lesions were summarized as follows: 39 (37.50%) colon polypoid lesions were type 1, 57 (54.81%) lesions were type 2 and 8 (7.69%) were type 3. There were no significant difference in the morphological characteristics of colon polypoid lesions between the different NICE types (P>0.05). The pathological examination showed that there were 38 non-neoplastic polyps (36.54%) and 66 neoplastic polyps (63.46%). The sensitivity, specificity and accuracy rate of colonoscopy for diagnosing the neoplastic polyps were 81.82%, 81.57% and 81.73%, respectively, while the values of NBI colonoscopy were 92.42%, 89.47% and 91.35%. The diagnostic efficacy between two methods were different (P<0.05). Further analysis showed that the diagnostic sensitivities of NBI colonoscopy for neoplastic polyps with the diameter<1cm and 1-2 cm were 92.59% and 92.31%, the specificities were 86.67% and 91.30%, and the accuracy rates were 90.48% and 91.94%. The consistency Kappa values of enteroscopy and colonoscopic NBI with results of pathology for the neoplastic polyps of different diameters were 0.793 and 0.829, respectively. The causes for misdiagnosing colon polypoid lesions by colonoscopic NBI were insufficient bowel preparations and blurred display of microstructure. Conclusions: Compared with the colonoscopy, the accuracy of NBI colonoscopy for diagnosing colon polyps is improved. The NBI colonoscopy is worth to be applied in clinical practice since it has high diagnostic value for colon polypoid lesions with the diameter <2 cm and also shows high accuracy for judging the characteristic of lesions with the diameter <1 cm.