Occasional black stools may be normal, but they may also be abnormal. If black stool occurs the patient should be followed up to see if they have recently consumed animal products such as pig’s blood, duck’s blood or if they have used drugs such as bismuth, including colloidal bismuth pectin, bismuth potassium citrate, bismuth aluminate, etc. If not, the stool routine plus occult blood test can be improved. If the occult blood is negative, consider it as peptic bleeding, which may come from the upper or lower gastrointestinal tract. The most common ones include peptic ulcer, colitis, and tumors, such as gastric cancer and colon cancer. To further clarify the diagnosis, gastroscopy as well as colonoscopy can be perfected.