 This study aimed to evaluate the efficacy of interferon α after prophylactic donor lymphocyte infusion DLI among high-risk acute leukemia patients undergone unmanipulated blood and marrow transplantation. Hematopoietic stem cell transplantation HSCT is an effective treatment option for high-risk acute leukemia AL. However, post-transplant relapse can occur in some patients, and the prognosis of these patients is usually very poor.Prophylactic DLI can decrease the risk of relapse of high-risk AL patients. Interferon α-2b exerts a relatively strong immunomodulatory effect. It can kill AL cells by regulating T-cell andor natural killer cell functions.Consequently, interferon α-2b may have potential value for high-risk AL patients after transplantation. The study hypothesis: Using interferon α-2b after prophylactic DLI following hematopoietic stem cell transplantation in patients with high-risk AL can further reduce relapse rate and improve leukemia-free survival. 