1.Blood in stool: It is the earliest and most common manifestation of colon cancer. In mild cases, it only shows a small amount of bleeding occasionally, which can only be known after laboratory test. Due to the different locations of the cancer, the bleeding volume and nature vary, and long-term bleeding may produce secondary anemia. 2.Abdominal pain: Some patients have persistent vague pain with inaccurate localization as the first or prominent symptom, while some patients only have abdominal discomfort or bloating. When colorectal cancer is combined with erosion, obstruction or secondary infection, due to the increase of peristalsis and spasm of the corresponding intestinal segment, obvious abdominal colic may appear. Some patients show typical incomplete intestinal obstructive abdominal pain, i.e. pain is paroxysmal colic, which lasts for several minutes, with self-conscious gas running through the pain, followed by exhaust, and then the pain suddenly disappears, when such symptoms appear in the elderly, colorectal cancer should be considered first. 3. Change in bowel habits: Most of them are changes in the number of bowel movements or stool characteristics, for example, the original stool was once a day, but recently, for unknown reasons, the stool is 3 to 4 times a day, or diarrhea and constipation alternate, and the shape of stool changes, originally the stool is soft and formed, but recently it suddenly looks like water, and there seems to be blood or pus in it. You should go to the hospital for a medical examination. (It should be noted that these symptoms are also common in other diseases, so a thorough physical examination should be performed if you have these symptoms). Some people also have a feeling of urgency, especially in young people. If there is no other reason (including travel, change of living environment and taking hyoscine, etc.) and constipation and diarrhea and other intestinal disorders often occur, and regular treatment is still ineffective for more than two weeks, it should be noted that it may be an early sign of colorectal cancer. 4.Anemia: Male patients, especially those without other causes of blood loss or intestinal parasitic diseases, should think of the possibility of stomach or colon cancer if they find progressive iron deficiency anemia.