Pain on the 21st day after anal fissure resection is usually abnormal. After anal fissure excision surgery usually about 2 weeks can be healed, the symptoms of pain will disappear, the patient in the 21st day after anal fissure excision pain is abnormal, usually due to the wound infection and the wound by the outside world stimulation and other reasons. If the patient for the wound infection, should be under the guidance of the doctor to take amoxicillin, levofloxacin, with anti-inflammatory and bactericidal effect, can alleviate the patient’s pain symptoms, allergic to drugs is prohibited; if the external stimulation is caused by the patient should avoid too much force in defecation, and pay attention to the cleanliness of the post-diarrheal period, lukewarm water baths, and the diet of light and easy to digest mainly. It is recommended that patients with the above situation, go to the hospital in time for review, to clarify the cause of the disease, listen to the doctor’s guidance and treatment, to avoid aggravation of the condition.