The incidence of colorectal cancer in China is on the rise, and in big cities, it has become the “oldest” of malignant tumors. In Shanghai, for example, the number of patients has increased more than five times in the past 30 years, and the incidence rate of young people has increased significantly. The more serious situation is that many people are found to have late stage colorectal cancer and the treatment effect is poor. Change in stool habit should be alerted To improve the efficacy of colorectal cancer, the key lies in early detection and treatment. The most common symptoms of colorectal cancer are blood in stool (48%~68%) and abdominal pain (21%~55%), which can generally attract people’s attention. However, another symptom, change in stool habit, is not sufficiently alarmed because it is common. In fact, changes in stool habits (including diarrhea, constipation, frequent stools, alternating diarrhea and constipation) are not uncommon among colorectal cancer patients, such as data from Shanghai: 28% to 50% of colorectal cancer patients have frequent stools; while data from Guangzhou show that 15% of patients have diarrhea and frequent stools, and those with constipation as the prominent symptom are also seen from time to time, especially in rectal cancer patients, it can be as high as 60%. Generally speaking, the number of bowel movements of healthy people is 1-2 times a day, or 1-2 times a day, mostly formed stools or soft stools; for a few people, the number of bowel movements can be up to 3 times a day, and the stools are mostly semi-formed or salami-like hard stools. In colorectal cancer patients, if the tumor stimulates the intestinal mucosa and leads to the exudation of body fluid, and the exudate accumulates too much in the intestinal lumen and stimulates the increase of intestinal peristalsis, diarrhea will occur. If the tumor is accompanied by inflammation, necrosis and causes obstruction in the intestinal lumen, it will prolong the passage time of feces and cause constipation. Diarrhea or constipation is determined by the location of the tumor. Whether diarrhea or constipation occurs is mainly related to the location of the tumor in the colon. The right side of the colon (including cecum, ascending colon and part of the transverse colon) has a wider lumen and is more mobile, so early stage cancer mostly manifests as diarrhea (about 20%), or alternating diarrhea and constipation. The left side of the abdomen (including part of the transverse colon, descending colon and sigmoid colon) is not as wide as the right side of the colon, and the sigmoid colon has a narrow lumen and is connected to the rectum at an acute angle, so once the tumor grows, it will mostly cause persistent constipation and frequent bowel movements, and is prone to chronic progressive intestinal obstruction. When the tumor appears in the rectum (rectal cancer), the ulcer on the surface of the tumor will stimulate the rectum and lead to frequent bowel movements, always wanting to defecate more than ten times a day, and the excreted stool becomes thin, with mucus, and the amount is also very small. Patients often have a feeling of incomplete defecation. Of course, changes in bowel habits are often influenced by the quality and type of diet, a variety of commonly used medications, infections with pathogenic microorganisms, and even mental and emotional factors. However, the occurrence of persistent and persistent diarrhea (including frequent bowel movements) or constipation, especially in those who have no previous bowel symptoms and those who are at high risk for colorectal cancer, should be taken seriously.