The pain inside the anus when defecating may be caused by hemorrhoids, anal fissure, perianal abscess and other diseases. 1. Hemorrhoids: the cause of hemorrhoids is not yet clear, it may be caused by prolonged sitting and standing, straining to defecate, unreasonable dietary habits and other factors. Patients may experience perianal pain, itching, blood in the stool and other symptoms, and when defecation can aggravate the symptoms of pain. 2. Anal fissure: when long-term constipation leads to the anal canal skin damaged under the effect of trauma, it will lead to the skin cracked throughout, forming ulcers. Or it may be caused by narrowing of the anal canal, reduced blood supply, infection, anal trauma and other factors. Patients may experience anal pain, blood in the stool and other symptoms. When the patient passes gas, the local mucous membrane is stimulated, which will aggravate the symptoms of pain. 3. Perianal abscess: Perianal abscess may be caused by infection, low immunity, trauma and other factors. Patients may have persistent pain and swelling around the anus, and if the exhaust may stimulate and pull the local mucous membrane, and pain occurs. There are many reasons that lead to pain inside the anus when exhausting, it is recommended that patients go to regular hospitals, identify the cause of the disease, and give reasonable treatment as soon as possible to avoid aggravating the condition.