The pain in the anus when you sit down may be caused by hemorrhoids, anal fissure, perianal abscess and so on. 1. hemorrhoids: the disease may be affected by genetic, dietary, defecation habits and other factors, will lead to the patient to sit down to the anus inside the pain of the situation, the patient is mainly manifested as blood, hemorrhoid prolapse, anal itching and other symptoms. 2. anal fissure: if the patient long-term constipation, fecal dryness, etc., will cause the patient in the defecation of mechanical trauma, leading to the patient appeared to sit down to the anus inside the pain of the situation, while the patient accompanied by constipation, bleeding situation. 3. Perianal abscess: a sit down inside the anus pain may be caused by perianal abscess, mainly due to purulent bacteria caused by anal gland obstruction, infection and so on, and accompanied by local swelling, pain, skin fever and other symptoms. It is recommended that patients go to the regular hospital in a timely manner, under the diagnosis of the doctor, according to the patient’s specific condition performance, targeted treatment, life should pay attention to keep the bowel movement, to avoid infection.