Bleeding in the stool and blood clots may be caused by internal hemorrhoids, upper gastrointestinal bleeding, colon cancer and other factors. 1. Internal hemorrhoids: internal hemorrhoids may occur when the hemorrhoidal veins become varicose. In the process of defecation, the stool may cause mechanical friction stimulation to the vein, which may lead to rupture of the vein, and if the bleeding volume is large, it may lead to bleeding and blood clots in the stool. 2. Upper gastrointestinal bleeding: when bleeding occurs in the upper gastrointestinal tract due to mechanical injury such as ingestion of foreign objects, cirrhosis of the liver, ulcer, with the peristaltic movement of the gastrointestinal tract, the blood may be discharged along with the stool, resulting in bleeding and blood clots in the stool. 3. Colon cancer: colon cancer is a kind of malignant tumor disease occurring in colon, tumor cells invade blood vessels, which can also cause bleeding, and when the bleeding volume is large, the blood will be clotted, and the symptom of bleeding and blood clots in stool may also appear. When there is bleeding and blood clots in the stool, one should consult doctor in time, and improve anal microscopy, gastroscopy, enteroscopy and other examinations under doctor’s guidance, so as to clarify the cause of the disease and treat it positively.