With the improvement of people’s living standard, the incidence of colonic and rectal melanosis has increased. This disease is less reported in China. The etiology and pathogenesis of colorectal melanosis are still not well understood. Patients with this disease can develop dielectric disorders, and the incidence of colorectal cancer and colorectal adenomatous polyps is high among patients with this disease. Therefore, in recent years, the occurrence, development and clinical manifestations of colorectal melanosis have been extensively studied in terms of etiology, immunity, cellular ultrastructure, and disorders of hydrophobic mediators, but the results are not consistent. There is less research on colorectal melanosis because of internal research. From 1984 to 1994, Changhai Hospital examined more than 13,000 patients with abdominal pain, diarrhea and blood in stool with fiberoptic colonoscopy, and detected 54 cases of colorectal melanosis. Now this part of patients is used as both the service object of diagnosis and treatment and as the research object, and the etiology and pathogenesis of the disease have been studied in depth. Treatment: Colonic and rectal melanosis is a reversible disease, and relieving the causes of constipation and difficult fecal evacuation, such as eating more vegetables and fruits and other foods containing more fiber, as well as drinking more water and exercising more, reduces constipation or difficult fecal evacuation. For the diseases that cause difficulty in defecation such as rectal protrusion, endorectal overturning and puborectal muscle syndrome, corresponding therapeutic measures should be taken, such as rectal protrusion repair, endorectal overturning fixation and puborectal muscle partial excision, in order to restore normal defecation and prevent the massive abuse of laxatives as an effective method for the treatment of melanosis. It has been reported that patients with colonic and rectal melanosis caused by long-term laxative use of rectal protrusion and endorectal sleeve, after rectal protrusion repair and endorectal sleeve fixation, had normal bowel movements, and the melanosis disappeared after 1 year of review after stopping laxative use. However, the treatment of patients with colon and rectal melanosis without laxatives must be further explored in the context of medical history, dietary habits, lifestyle and other characteristics.