Common blood in stool painless bright red may be due to hemorrhoids, anal papilloma, rectal polyps, rectal cancer, constipation, abnormal coagulation function and other reasons. 1. Hemorrhoids: internal hemorrhoids patients because of poor bowel movement, dry and hard stool scratch hemorrhoidal nucleus surface mucosa, causing rupture bleeding, usually manifested as painless bright red bleeding. 2. anal papilloma: mainly caused by bacterial or viral infections, common manifestations of anal papillary hyperplasia, edema, etc., often appearing in bowel movements, pressure, painless bleeding. 3. Rectal polyps: when there is ulceration or damage on the surface of rectal polyps, there will be painless and bright red blood in stool. 4. Rectal cancer: rectal cancer usually refers to malignant tumor of rectal mucosa epithelial cells, and the surface of cancerous tumor is prone to ulceration and bleeding, and then there will be blood in stool without pain and bright red. 5. Constipation: when constipation is caused by straining to defecate, it may lead to tearing of anal mucous membrane, and then blood in stool will be painless and bright red. 6. Abnormal coagulation function: when the human body is subjected to disease factors, drug factors or other triggering factors, such as hemophilia, primary thrombocytopenic purpura and other diseases, there may be abnormal coagulation function, blood in the stool without pain. When the phenomenon of painless bright red blood in the stool, it is recommended that patients seek medical attention to identify the cause of the bleeding, under the guidance of the doctor for appropriate treatment.