Inclusion Criteria:  Patients suffering from high horseshoe anal fistula  Exclusion Criteria:  Specific cause of fistula e.g. Crohn's disease. Previous anorectal surgery. Patients with malignant tumors or mental illness or other reasons unable to cooperate with the treatment. Patients with serious primary diseases such as tumor, malnutrition, endocrine and hematopoietic system.