The probability of having a positive fecal occult blood for cancer cannot be determined, and a variety of factors can lead to a positive fecal occult blood. Cancer of the digestive tract can lead to positive fecal occult blood, other factors, such as hemorrhoids, anal fissure, peptic ulcer, blood diseases, schistosomiasis, systemic diseases, such as leukemia, thrombocytopenic purpura, hemophilia and so on, can lead to positive fecal occult blood. In the early stage of GI cancer, a few patients will have positive fecal occult blood, and in the late stage of GI cancer, most of the patients will have positive fecal occult blood, which is persistently positive. In order to confirm the diagnosis of GI cancer, it is necessary to do the examination of pathologic analysis, colonoscopy or gastroscopy, and so on. In order to exclude digestive tract cancer, patients with positive fecal occult blood need to do further examination in a timely manner, do not be negligent to avoid delaying the condition, and patients should not self-medication.