Abstract To explore the clinical application value of narrow band imaging (NBI) in the early screening of colorectal cancer. 200 patients were selected as the research objects, and were divided into test group and control group by the randomization method, within 100 cases in each group. The patients in the test group were examined by NBI, while the patients in the control group were examined by ordinary endoscopy, and then the lesion detection rate, image definition and pathological examination results of the two groups were compared. After the patients in the test group received NBI examination, the lesion detection rate, image definition and lesion detection coincidence rate were significantly higher than those of the control group, and the comparative difference between the two groups was statistically significant (P < 0.05). NBI examination of colorectal mucosa can clearly show the pit pattern and the morphological structure of capillaries of the early colorectal cancer and its precancerous lesions, thus effectively improving the diagnosis rate of early colorectal cancer and its precancerous lesions, playing a good clinical application value in the early screening of colorectal cancer, and guiding the later treatment, so it is suitable for clinical promotion.