An anal exam typically detects 70% of rectal cancers. Anal examination is the use of a person’s finger to do anal diagnosis, also known as anal finger diagnosis. Anal diagnosis is relatively simple, can be checked at any time, and the cost is relatively low. Generally, outpatient doctors are required to try to do anal diagnosis for checking in case the patient does not agree to do colonoscopy or does not have the condition to do colonoscopy so as not to miss it. The length of the finger is usually around 8cm, which can only touch rectal cancer with diameter ≤8cm, and cannot touch tumors more than 8cm, which may be misdiagnosed. Nowadays, doing anal examination for rectal cancer is less and less compared to 10 or 20 years ago, and the most accurate clinical recommendation is still to go for colonoscopy. Therefore, once anal symptoms appear, anal examination is a good method, but it can not replace colonoscopy, CT, MRI and other auxiliary examinations, and it is recommended that patients go to specialized outpatient clinics to do a number of specialized examinations, so as to prevent the leakage of rectal cancer diagnosis.