There are no obvious symptoms in early stage of colorectal cancer, and clinical symptoms will appear only when the disease progresses to a certain degree, which are mainly as follows: 1. Bowel irritation and change of bowel habit: frequent bowel movement, diarrhea or constipation, sometimes constipation and diarrhea alternately, acute and severe bowel movements, anal distension, abdominal pain and so on. 2, blood in stool: sometimes bright red, sometimes dark red, usually intermittent, sometimes mucous blood stool, or accompanied by blood clots. 3, Bowel obstruction: it is the manifestation of advanced stage of colorectal cancer. 4, Lump felt in abdomen: it usually means that the tumor has developed to a certain degree. 5, Systemic symptoms such as anemia, emaciation, fatigue and so on: usually late stage manifestations. The diagnosis of colorectal cancer is mainly based on the above manifestations as well as physical examination by doctor and necessary tests, such as colonoscopy, abdominal plain film, ultrasound, CT or magnetic resonance test, blood tumor marker test, etc., of which the most important one is to perform colonoscopy and take biopsy for clear pathological diagnosis, which is the gold standard for final diagnosis, followed by staging, and necessary genetic test as appropriate, in order to clarify molecular staging and to guide the subsequent treatment. Then the staging will be done.