Colon cancer and rectal cancer are malignant tumors occurring in the mucosal epithelium of the colon or rectum, and due to the similarity of their pathogenesis and principles of diagnosis and treatment, they are often combined and collectively referred to as colorectal cancer in medicine. The total length of adult colon is about 1.5m, including cecum, ascending colon, transverse colon, descending colon and sigmoid colon, which is connected to rectum and anal canal (Figure 1). According to the 2016 Big Data Study on Analysis of Incidence and Death of Malignant Tumors in China, it was reported that there were 331,000 new cases of colorectal cancer in China each year, ranking fourth in incidence rate among all malignant tumors; 159,000 patients died from the disease each year, and the mortality rate ranked fifth in causes of cancer death. Colorectal cancer has become the third most prevalent malignancy in the United States, with more than 106,000 people diagnosed with colorectal cancer each year. Unlike our country, despite the high incidence of colorectal cancer in the United States, the mortality rate has been decreasing year by year, mainly due to the fact that more and more colorectal cancers are detected at an early stage and thus have a chance to be cured. In contrast, patients with colorectal cancer in China often seek medical diagnosis only after symptoms such as abdominal pain, blood in stool, change in stool habit and severe anemia appear, at which time the tumor is already in the middle and late stages, losing the best time for early treatment and cure, and the curative effect is often unsatisfactory. Therefore, it is very important for adults over 40~45 years old to have regular medical checkups and colorectal tumor screening, especially for those who have family members suffering from colorectal cancer or other malignant tumors. The cure rate of early colorectal cancer is above 90%; and only surgical resection or endoscopic resection alone is required, and radiotherapy and other treatments are generally no longer needed, and the pain and medical expenses experienced by patients will be significantly reduced.