In general, the general population can have annual anal finger examination and fecal occult blood examination after the age of 40, sigmoidoscopy every 5 years after the age of 50, or barium enema combined with colonoscopy every 5 to 10 years. However, people with gastrointestinal symptoms over 30-40 years old, middle-aged and elderly people in big cities, people with family history of colorectal cancer or white-collar people with unbalanced dietary structure are all high-risk groups of colorectal cancer. It is recommended that high-risk groups should receive colonoscopy every 3 to 5 years starting from the age of 40. The following are the initial screening measures for high-risk groups.