Diarrhea with blood in the stool after meals may be due to hemorrhoids, anal fissure, ulcerative colitis and other diseases. 1. Hemorrhoids: usually due to improper diet, sedentary and other factors leading to the emergence of substantial venous clusters in the perianal skin, at mealtime, when consuming too spicy and stimulating food, may lead to abnormal peristalsis speed, so that the stool is too dry, hard, so that there is a stool with blood when defecating, accompanied by diarrhea phenomenon. 2. Anal fissure: it is usually a small ulcer formed after the skin layer of the anal canal below the dentate line is cracked. When defecating, it is too hard, and the phenomenon of blood in the stool may also occur. When eating, improper diet may lead to abnormal gastrointestinal function, resulting in the phenomenon of diarrhea. 3. Ulcerative colitis: the cause of this disease is not clear, may be related to genetic bacteria, infection and other factors, its clinical symptoms are mostly manifested as bloody diarrhea. Diarrhea after meals with blood in the stool may also be other reasons, such as rectal tumors, polyps, etc., it is recommended to go to the hospital in a timely manner for examination, to identify the cause of the disease, to take targeted treatment.