Early screening for colorectal cancer includes the following aspects: 1. Annual screening is recommended for middle-aged and elderly people over 45 years old, and the screening includes stool OB test to determine whether there is potential bleeding in the intestine based on positive or not; 2. Blood sampling for tumor markers, such as CEA, CA199, CA242, etc., which need to be combined with several indicators at the same time; 3. Anal finger examination is an easy and effective way to detect colorectal cancer, which must be done in a specialized hospital; 4. Colonoscopy and biopsy can be performed to confirm the diagnosis of adenoma, polyp or colorectal cancer.