Early colorectal cancer is often asymptomatic, and symptoms appear only when the tumor increases and complications occur. According to domestic data, the first complaint of colorectal cancer patients is blood (48.6%), especially rectal cancer patients, followed by abdominal pain (21.8%), with colon cancer patients being the most common. 1.Blood in stool is the earliest and most common manifestation of colon cancer. It is often misdiagnosed as dysentery or hemorrhoid bleeding and misses the time to confirm the diagnosis. 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 is the first or prominent symptom of some patients with inaccurate localization of persistent vague pain, while some patients only have abdominal discomfort or bloating. When colorectal cancer combined with erosion, obstruction or secondary infection, due to increased peristalsis and spasm of the corresponding intestinal segment, obvious abdominal colic may appear. Some patients have diarrhea as the first and main symptom, or constipation, or alternating diarrhea and constipation. The stool may be mucus and blood, mucus and pus and blood, or thin stool. Some people also have a feeling of urgency, especially when it occurs in young people. If constipation, diarrhea and other intestinal disorders often occur without other reasons (including travel, change of living environment and taking hyoscine, etc.), 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.Male patients with anemia, especially those without other causes of blood loss and intestinal parasitic diseases, should think of the possibility of stomach cancer or colorectal cancer if they are found to have progressive iron deficiency anemia.