Colorectal cancer is a common malignant tumor of the gastrointestinal system, including colon cancer and rectal cancer, and rectal cancer has the highest incidence rate. The cause is unclear and may be related to living habits, diet, environmental factors and autoimmune factors. Early clinical symptoms of colon cancer are not obvious, or there are only abdominal distension, abdominal pain, change of stool habit, etc., mostly due to gastrointestinal tract dysfunction or intestinal obstruction, and mostly occur in the lower and middle abdomen, with hidden pain, and the symptoms gradually worsen, and there can be blood in the stool, often in the state of blood and stool separation, if the disease progresses and the symptoms worsen, there will be anemia, emaciation, fever, etc., through colonoscopy and imaging examination can generally The diagnosis can be made clearly through colonoscopy and imaging examination, and pathology can be done if necessary, and the treatment is mainly surgical treatment, and the specific treatment plan needs to be judged according to the tumor site and histopathological type as well as the scope of cancer. In the early stage of rectal cancer, there will be change in stool habit or stool shape, and there will also be symptoms such as diarrhea, constipation, blood in stool, urgency, etc. If the disease develops further, abdominal pain and intestinal obstruction may also appear. In conclusion, if there are unexplained changes in stool habits, such as diarrhea, constipation and blood in stool, you need to go to the gastroenterology department of the hospital for colonoscopy in time for early detection and treatment, and you need to eat a vitamin-rich and high-protein diet, and prohibit cold, hard and spicy food.