Bleeding from the anus without defecation is a type of lower gastrointestinal bleeding. There are many causes of lower gastrointestinal bleeding, including small bowel diseases, colon diseases, rectal diseases, and systemic diseases. Small intestine diseases include small intestine diverticulum, small intestine inflammation, small intestine tumor, colon diseases include colon tumor, colon inflammation, rectal diseases include hemorrhoids, anal fissure, rectal tumor, and systemic diseases include hematologic diseases and blood clotting disorders, which can be manifested as bloody stools, or as no defecation and only anal bleeding. The occurrence of anal bleeding should be taken seriously and the corresponding examination should be improved as soon as possible to clarify the location and nature of the disease, and then targeted treatment.