Rectal cancer is a common malignant tumor of the gastrointestinal tract, and the proportion of rectal cancer among young people in China is high, about 10% to 15%. Cancer is caused by the interaction of many different factors, such as environment, nutrition and diet, genetics, viral infection and lifestyle choices, etc. 1/3 of cancers can be prevented and 1/3 of cancers can be treated if diagnosed early, especially rectal cancer. The main measures to prevent rectal cancer are: 1. reasonable diet and prevention of constipation. High-fat and high-protein food can increase methylcholanthrene in stool, which can induce colon and rectal cancer. Less fiber food slows down the speed of stool passing through the intestine, which increases the contact time between carcinogenic substances and intestinal mucosa. 2.Actively treat chronic inflammation of the rectum. Such as ulcerative colorectitis and schistosomiasis can cause repeated destruction and repair of intestinal mucosa and carcinoma, which should be treated actively. 3.Early treatment of precancerous lesions. Such as rectal adenoma and polyposis have a high rate of malignant transformation and must be treated by early surgery. Rectal cancer metastasis is late, early radical surgery can be cured, which depends on the early detection of rectal cancer. Patients do not pay enough attention to symptoms such as blood in stool and change in stool habit, and doctors are not vigilant enough, which leads to delay in treatment. There are the following methods for early diagnosis of rectal cancer: 1. To perform fecal occult blood test for high-risk groups, and further examination for those who are positive. 2.Patients with symptoms such as blood in stool, change of stool habit and stool deformation must undergo rectal finger examination, and more than 75% of rectal cancer can be palpated during finger examination. More than 75% of rectal cancers can be palpated during finger examination. 3. If cancer cannot be palpated during rectal finger examination but is highly suspected, endoscopic examination should be performed and biopsy should be taken for pathological examination after the mass is found.