Rectal cancer lacks symptoms in the early stage, and patients have no obvious abnormal changes. When the mass reaches 1~2cm, due to the erosion of the tumor, the intestinal mucosa suffers from foreign body stimulation of the mass and the secretion increases, so a small amount of mucus is discharged during defecation, mostly at the front of the stool or attached outside the stool. As the tumor increases, the mucus secretion also increases. Sometimes, with the increase of intra-abdominal pressure by exhaustion or sudden coughing, mucus may flow out from the anus. When the tumor increases and forms ulcers or necrosis combined with infection, there will be obvious symptoms of rectal irritation and changes in the number of bowel movements and nature of stool. The number of bowel movements increases, 2 to 3 times a day, with mucus stool, thin stool, mucus and blood stool. It is often misdiagnosed as enteritis, dysentery, ulcerative colitis, etc. However, the diarrhea symptoms of rectal cancer are not like colitis, which has a rapid onset and quick improvement; nor is it like dysentery, which has typical symptoms of urgency. The rectal irritation symptom of rectal cancer is slow and progressive, and the irritation symptom is obvious when combined with infection, but it can be temporarily improved after symptomatic treatment, but those who still have mucus and blood stool after longer treatment should be paid enough attention. The patient should go to the hospital for detailed examination when the following conditions occur ① Abnormal stool habits, increased frequency of bowel movements, along with a small amount of mucus stools, mucus blood stools, those who do not improve after treatment, or those who improve after treatment but relapse, should be promptly diagnosed and treated. (2) If there is a history of mucus stool or diarrhea, but the symptoms are mild and suddenly increase, and the number of bowel movements and nature of bowel movements change, the diagnosis should be confirmed by re-examination. ③If constipation and diarrhea alternate without obvious reasons and do not improve with short-term treatment, and if no abnormality is found in the stomach after barium fluoroscopy, the rectal area should be examined in the hospital. ④Straining to defecate, the expelled stool has pressure marks, grooved flat stripes, thin strips …… must be done rectal examination. Any of the above four conditions should be promptly checked in the hospital. Where available, it is best to ask a surgeon or anorectal surgeon for an examination.