Colorectal cancer is a common malignant tumor, and the incidence rate in developed countries is high because the incidence of colorectal cancer may be related to high-fat and low-fiber diet. The incidence rate in China has also increased, and with the change of people’s diet structure, the improvement of refinement, as well as the acceleration of work pace, the increase of life pressure and the aggravation of environmental pollution, the incidence rate has further increased and the trend of youthfulness. Like any malignant tumor, early detection and early treatment is the only way to improve the long-term survival rate of colorectal cancer, such as according to Dukes stage, 5-year survival rate: stage A: 90%, stage B: 75%, stage C: less than 50%, stage D: less than 10%, which shows the importance of early diagnosis and treatment. Early stage generally refers to Dukes stage A, that is, T12N0M0 of TNM stage, which means that the tumor only invades the submucosa and lamina propria, and such early stage cancer still has 10% of local lymph node metastasis, and in recent years, more attention has been paid to the study of in situ cancer limited to mucosa, which can be completely cured from no lymph node metastasis. However, because early colorectal cancer has no uncomfortable symptoms or light symptoms, it cannot attract patients’ attention, so there are only a few early stage patients in the clinic, which means that the diagnosis of early colorectal cancer is still a problem that has not been properly solved, and if patients come to the doctor only when symptoms appear, it is obviously not early. 2. High risk factors of colorectal cancer Early detection should start from the high-risk group, and the possibility of colorectal cancer is higher than the general population with the following conditions: (1) Family history: Those with family history have 2~3 times higher chance of colorectal cancer than the general population. Familial adenomatous polyposis (FAP) all have APC gene deletion, which can become cancerous after the age of 40 and almost 100% cancerous at the age of 55. This disease is rare and accounts for only 1% of all colorectal cancers. Hereditary non-polyposis (HNPCC) is caused by mismatch repair gene mutation, accounting for 5%~10% of colorectal cancer, which develops earlier than the general population and can develop cancer after 20 years old. (2) History of polyps or polyp surgery: mainly refers to adenomatous polyps, which have 2-5 times higher chance of cancer than those without polyps, and the incidence of cancer in multiple cases is 1 times higher than that in single cases. (3) Patients with history of radiotherapy for gynecologic tumors have 2~3 times higher chance of developing cancer, and the incidence rate increases year by year after 40 years old. (4) Those with previous history of colorectal cancer surgery. The chance of second primary colorectal cancer is 3 times higher than that of the general population, and female patients with breast cancer or gynecological tumors are also more likely to develop colorectal cancer than the general population. (5) Patients with long-term chronic colitis. The incidence of colorectal cancer is 3% in the first 10 years and increases by 20% every 10 years thereafter. (6) Middle-aged and elderly people over 40 years old who have unexplained changes in stool habits (such as mucus stool, mucus-purulent-blood stool, black rim, increased or decreased frequency of stool, change in stool shape, feeling of incomplete stool, etc.) or abnormal stool. Those with the above conditions should not be taken lightly, and surgeons should be vigilant that they do not miss the high-risk factors for early diagnosis of colorectal cancer. The American Cancer Society (ACS) recommends that people over 40 years old should go to the anorectal department of hospital for rectal examination once a year, and those over 50 years old should have fecal occult blood examination and colonoscopy once every 5 years. For high-risk groups, the age of routine checkups should be advanced by 10 years, and annual colonoscopies should be sought. Currently, fecal occult blood test (FOBE) is the most simple, economical and positive test, and it can be used as the main method for screening and investigation. Strictly speaking, positive fecal occult blood means that there is a break in the mucosa and it is no longer early, but there is no better way to do this. A formal FOBE is performed on three consecutive days, with samples taken at different points of the stool specimen. Secondly, anal finger diagnosis is also a simple and effective method: experienced specialists should not ignore the significance of finger diagnosis, which is also known as “finger eye” and can distinguish the presence or absence of tumor, its size, texture, smoothness, mobility and other characteristics. Thirdly, e-colonoscopy is an important equipment for diagnosis and treatment of colorectal cancer: e-colonoscopy uses light-guiding fiber and electronic collection equipment to transform the collected optical signal into electronic signal in the form of graphic display to the doctor and patient, which can not only visually observe the morphology of the lesion, but also take biopsy for characterization and perform submucosal resection (EMR) for early colorectal cancer. Therefore, e-colonoscopy is more and more widely used in the diagnosis and treatment of colorectal lesions. With the improvement of China’s medical level and the enhancement of people’s awareness of self-care, the scope of population screening will be expanded and the quality of screening will be improved, and more early colorectal cancers can be detected, which will further improve the long-term survival rate.