Positive fecal occult blood suggests the presence of gastrointestinal bleeding, but it cannot directly indicate whether the cancer is early or late, and the common causes include: gastroenteritis, peptic ulcer, and gastrointestinal tumor. 1. Gastroenteritis: often accompanied by fever, abdominal pain, diarrhea and other discomforts, in addition to a positive fecal occult blood, usually need to be based on symptoms, blood tests and other tests to clarify. 2. Peptic ulcer: gastric ulcer and duodenal ulcer may be manifested as positive fecal occult blood, accompanied by abdominal pain, abdominal distension and other discomforts, and need to undergo gastroscopy for clear diagnosis. 3. Gastrointestinal tumor: gastric cancer and colorectal cancer may show positive occult blood in stool, but positive occult blood cannot indicate early or late stage of cancer, so gastrointestinal microscopy, abdominal CT or MRI, biopsy and other examinations are needed, and if necessary, surgery and pathological examination can clarify the tumor staging, and the patient can be treated with surgery and chemotherapy. It is recommended that the patient go to the hospital in time, identify the cause of the disease and follow the doctor’s instructions for treatment.