The human digestive tract is divided into two sections; the upper section is called the upper GI tract and the lower section is called the lower GI tract. The upper GI tract generally refers to the esophagus, stomach and duodenum, while the lower GI tract includes the jejunum, ileum, colon and rectum. The duodenum, jejunum and ileum are all part of the small intestine; the colon and rectum are part of the large intestine. The large intestine starts from the ileocecal valve and ends at the anus, which is the largest intestinal cavity in the human body, hence its name. According to the location and characteristics of the large intestine, we can roughly divide the large intestine into three parts, one is the right half of the colon, the second is the left half of the colon, and the third is the rectum and anus. The rectum is the most terminal part of the human gastrointestinal tract (about 12-15 cm long, and the general surgeon’s index finger is about 10 cm long, and most rectal cancers can be detected by the clinician with finger diagnosis); the anus is the last portal of the large intestine (surrounded by two layers of internal and external sphincter muscles, which control the excretion of stool), and is also the first part of the colonoscopy. If the entire digestive tract is compared to a tunnel, the large intestine is the last section of this tunnel. In this tunnel, the chyme passes slowly and finally forms stool in the large intestine and is expelled through the anus. Colon cancer is one of the most common malignant tumors of the gastrointestinal tract, mostly occurring in middle-aged and elderly people over 50 years old, but recently there is also a trend of younger age. In recent years, the incidence of this disease has a rising trend. This may be mainly related to the factors of changing dietary habits: with the increasing standard of living, people’s intake of fine foods, animal fats and proteins has increased, coupled with the accelerated pace of life and shortened eating time, resulting in the body’s failure to take in sufficient amounts of fibrous foods, causing toxic substances to accumulate in the colon for a longer period of time, breeding flab and transforming into cancer cells. Since the clinical biological characteristics of young people are different from those of middle-aged and elderly people, the underdiagnosis rate of colorectal cancer in young people is higher, and it is usually found at an advanced stage. Different parts of colorectal cancer have their own special manifestations and symptoms. Once patients find the corresponding manifestations and symptoms, they should seek medical attention as soon as possible. Early detection, early diagnosis and early treatment of colorectal cancer are very important. Because the early treatment effect of colorectal cancer is good, the 5-year survival rate reaches 60% to 70%, and some of the patients can survive for a long time and work normally after surgery. However, if the early treatment opportunity is missed, metastasis to liver or other organs will occur, and then the treatment effect is very unsatisfactory. So far, colonoscopy is still the only test that can detect colorectal cancer more accurately, so in any case, patients with indications should still receive the test.