Colorectal cancer has become one of the major tumors threatening human health, and its incidence rate is increasing year by year. It has become imperative to treat colorectal cancer correctly, how to detect it early, diagnose it early, and finally treat it early for patients. We find that many patients are already in the progressive stage of colorectal cancer when they come to our hospital. In fact, if timely diagnosis and intervention are given when patients first appear to be unwell, the prognosis of patients will be greatly improved. What are the manifestations of colorectal cancer? Colorectal cancer grows relatively slowly and is often asymptomatic or asymptomatic specific in early stage, which is easy to be ignored, and as the tumor grows, its symptoms gradually show up, however, when obvious symptoms appear, it is often not early. At the same time, because of the differences in anatomy, physiological function and tumor pathological characteristics, the clinical manifestations of colorectal cancer in different parts of the body are different. The caliber of right colon is larger, the intestinal wall is thin, and the intestinal contents are mostly liquid. Moreover, right hemicolectomized colon cancer mostly grows into the intestinal cavity, and the distal end of the tumor is prone to ischemic necrosis, bleeding and secondary infection, so clinically it often manifests as anemia, weakness, poor appetite, emaciation, fever, vague pain in the right side of the abdomen, and right abdominal mass, but there is no bowel habit or other intestinal symptoms. The caliber of the left hemicolectomy is thinner than that of the right side, and the contents are mostly semi-solid, while the cancer in the left hemicolectomy grows in an infiltrative form, and the infiltrative type is more common. Therefore, change in bowel habit, blood in stool, mucus stool, abdominal pain and intestinal obstruction are common, and systemic symptoms are rare. In contrast, most of the early stage of rectal cancer shows blood in stool and change of bowel habit, and then chronic obstruction symptoms gradually appear, and when the tumor invades the perianal area or adjacent organs, it shows corresponding clinical symptoms. Don’t ignore the significance of rectal finger examination Anorectal finger examination can generally detect middle and lower rectal cancer within 8cm from the anus, and it can also determine the surrounding tissue invasion and resectability of middle and lower rectal cancer. In addition, anorectal examination can also detect the implantation and metastasis of colorectal cancer in other parts of the abdominal cavity. According to incomplete statistics, about 80% of rectal cancers are detected by rectal examination, while 80% of misdiagnosed rectal cancers are not detected by anorectal examination. Therefore, when colorectal diseases are suspected, standardized anorectal examination should be performed, and the importance of rectal examination should not be ignored. Fecal occult blood test (FOBT) is an economical and effective method Fecal occult blood is one of the most common early indicators of colorectal cancer, which has an irreplaceable role in screening and early diagnosis of colorectal cancer. However, it is still widely used for screening colorectal cancer in high-risk groups and general population over 50 years old because of its non-invasive, simple, effective and cheap advantages. Fiberoptic colonoscopy is particularly important for colorectal cancer diagnosis. The application of fiberoptic colonoscopy is an important progress in colon cancer diagnosis, which can directly observe the lesions and take biopsies for pathological examination. At the same time, colonoscopy can deal with some lesions under the microscope and treat the adenomas found during the examination in time. Therefore, colonoscopy is the most reliable method for clinical diagnosis of colorectal cancer. The purpose of colon cancer screening is prevention The American Cancer Society recommends regular medical checkups for the general population after the age of 50 ① One FOBT examination every year, and full colonoscopy or double contrast barium enema for positive cases. ②1 fiberoptic sigmoidoscopy every 5 years. ③1 double contrast barium enema every 5 to 10 years. ④1 full colonoscopy every 10 years. In recent years, it has been advocated that barium enema should be used as a diagnostic test instead of colonoscopy only when there is no condition for colonoscopy. In the examination of high-risk groups of colorectal cancer, it is generally required that patients with colorectal cancer should undergo a full colonoscopy once a year after surgery, and those who have no abnormal findings in 3 years can be examined once every 2~3 years for the rest of their lives. In this way, multiple primary colorectal cancers in different times can be detected in time. For family members with one first-degree relative at high risk of colorectal cancer, rectal finger examination and fecal occult blood examination should be done every year from the age of 35, and full colonoscopy every 3~5 years from the age of 40. If two of the first-degree relatives have colorectal cancer, or if someone has colorectal cancer before the age of 40, the above examination should be started earlier, and colonoscopy should be done every two years. In conclusion, through meticulous medical history, careful physical examination, comprehensive analysis of patient’s characteristics, reasonable auxiliary examinations, emphasis on rectal examination, fecal occult blood and colonoscopy, misdiagnosis and leakage can be reduced, and through early diagnosis of colorectal cancer, it is expected to prolong patient’s survival and improve patient’s quality of life.