Objective Studying the effect of melanosis coli (MC) on colonic polyps.Methods This is a reospectively review of patients with electronic colonoscopy in our hospital from January 2014 to January 2017. A total of 522 cases of colorectal melanosis (MC) were composed of MC group, and 569 patients were randomly selected to form a non-mc group. The comparison of basic information between the two groups and the relationship of colon polyp and colon cancer was analyzed.Results The median age of the colon melanosis group was 64 years (51~73 years old), and the median age of the non-colonic melanosis group was 54 years (47 to 64 years old), with no statistically significant differences between the two groups.The detection rate of colon polyps in MC group was 47.8%. The detection rate of colon polyps in non-mc group was 40.2%, P= 0.013, and the difference was statistically significant.The two groups of polyps had the lowest detection rate of inflammatory polyps in pathological types, and the detection rate of adenomatous polyps was up to 58.0% and 51.5% respectively, but there was no statistically significant difference between the two groups. In the cecum, the detection rate of the descending colon was low, and the detection rate of multiple sites, rectum and sigmoid colon was relatively high, but the difference was not statistically significant.The size of colon polyps was concentrated in the range of 0~9 mm, and the percentages of the two groups were as high as 92.0% and 91.3% respectively, while the detection rate of the size being more than 20mm was low, that is 0.40% and 0.44%. But there was no statistical difference between the two groups.Conclusion The detection rate of polyps in MC group was higher than that in non-mc group, and the difference was statistically significant.There was no statistically significant difference between the two groups of colon polyps pathology, pathogenesis, and polyp size.