As people’s living conditions improve and dietary habits change, the incidence of bowel cancer is on the rise, especially in some large cities where the incidence of bowel cancer is significantly higher than in rural areas. Colonoscopy is the best way to detect bowel diseases at an early stage. However, many patients do not know much about colonoscopy and have a sense of fear, which makes them refuse to undergo colonoscopy. It is this fear that makes many patients delay their condition and miss the chance of recovery that they could have had for nothing. Clinically, we often come across cases of delayed treatment due to fear of undergoing colonoscopy, which is really a pity. Some people wrongly believe that “as long as the blood in the stool stops, everything will be fine”, which leads to a delay in the diagnosis of bowel cancer or precancerous lesions, and failure to get effective and less traumatic treatment. There are also those who had been diagnosed as bleeding hemorrhoids or enteritis when they initially had blood in stool, and refused to undergo colonoscopy when they bled again later on, and still delayed the diagnosis by explaining it as bleeding hemorrhoids or enteritis. The medical profession in the United States has proposed that asymptomatic people over the age of 50 should have their first bowel health check. In the Asia-Pacific region, the Colorectal Cancer Working Group pointed out at the “Asia-Pacific Consensus on Colorectal Cancer” meeting held in Hong Kong in September 2007 that colorectal cancer screening should be conducted after the age of 50 years. It was also pointed out that people in certain parts of Asia (e.g. China, Japan, Korea) are more susceptible to colorectal cancer than people elsewhere. And in China, because bowel cancer develops earlier than in the West, the first colonoscopy to screen for bowel cancer should be done earlier than 40 years of age for Chinese people. Colonoscopy, the main medical equipment for checking intestinal diseases, is a 130-cm-long, bendable, fiber hose with a light source at the end with a miniature electronic camera. It slowly enters the large intestine through the anus and reaches the end of the small intestine to examine the lesions in the large intestine and the end of the small intestine. Compared to x-ray, CT, MRI and gastroscopy, colonoscopy is a little unfamiliar to people. With the improvement of the performance of colonoscopy and the operation technique, the indication of colonoscopy has become more and more relaxed, and more and more accepted by patients and medical checkups. Generally speaking, all suspected lesions of the large intestine or the end of the ileum and failed to make a clear diagnosis, such as no contraindications to the examination, are feasible enteroscopy. Colonoscopy is intuitive, clear, and can also biopsy the suspicious parts, and if necessary, can also be instant endoscopic treatment, its superiority is obvious, is other means of examination can not be replaced. Through colonoscopy, early-stage bowel cancer without symptoms can be detected for timely treatment; early-stage bowel cancer can be detected and part of it can be resected simply under colonoscopy to avoid the trauma of surgical treatment; pre-cancerous lesions such as adenomatous polyps can be detected and resected under colonoscopy, thus blocking the process of its development to bowel cancer and achieving the purpose of preventing cancer.