Abstract： Objective To explore the safety and efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in refractory or relapsed leukemia patients undergoing total body irradiation and FLAG regimen consisting of fludarabine,cytarabine,granulocyte colony stimulating factor (TBI/FLAG).Methods Forty-seven cases of refractory or relapsed leukemia treated in our hospital between May 2012 and December 2015 were analyzed retrospectively,including 14 cases of acute lymphoblastic leukemia,31 cases of acute myeloid leukemia,2 cases of acute transformation of chronic myelocytic leukemia.All patients did not achieve remission before bone marrow transplantation.The proportion of blast cells was 10％-98％.The TBI/FLAG was the main conditioning regimen.Kaplan-meier curve was used to analyze the cumulative incidence of GVHD,cumulative recurrence rate,overall survival rate (OS) and disease-free survival rate (DFS).Results Of 47 cases,there was only one patient with infection during the preconditioning and the cell engraftment was not successful,and the rest 46 patients were successfully engrafted.The median time of leukocyte engraftment was 17 (11-25) days,and the median time of platelet engraftment was 21 (11-70) days.The cumulative incidence of acute GVHD was (62.3 ± 7.3)％,including 51.1％ and 28.4％ in Ⅱ and Ⅲ-Ⅳ grade respectively.Twenty-four patients suffered chronic GVHD in 44 assessable patients,and the cumulative incidence was (77.1 ± 11.2)％.The bone marrow was assessed 28 days after transplantation,and the results showed that 46 patients achieved complete remission,and DNA test confirmed complete donor chimerism.The median follow-up time was 12 (1-44) months,25 patients survived (53.19％,25/47),and 13 relapsed (27.65％,13/47).The 1-yearOS and DFS was 47.9％ and 45.5％ after transplantation.Conclusion TBI/FLAG-based regimen is safe and effective for refractory or relapsed leukemia,and the major risk still is relapse for refractory or relapsed leukemia patients after transplantation.The method of preventing recurrence needs to be further explored.