[Objective]To discuss the clinical effect of fludarabine and busulfan (Bu+Flu) as a low toxicity myeloablative conditioning regimen for allogeneic peripheral blood stem cell transplantation (allo-HSCT)in leukemia patients.[Methods]Clinical data of 13 patients with hematological malignancies receiving conditioning regimen with Bu+Flu for allo-HSCT were analyzed retrospectively.Conditioning regimen was Bu+Flu,compalriot mismatched and unrelated transplantation combined with rabbit anti-human thymocytes immune globulin (ATG).CsA+short course of methotrexate or CsA + mycophenolate mofetil were used to prevent graft-versus-host disease (GVHD).DNA sequencing of short tandem repeat (STR)polymorphism analysis method was performed for identification of donor stem cells implantation.[Results]13 patients all tolerated with this conditioning regimen well,no serious complications occurred.Neutrophil engraftment was at 9-15 days (median 11 days),platelet engraftment at 8-25 days (median 13 days).10 patients achieved hematopoiesis reconstitution with their full donor chimerisms confirmed by STR-DNA analysis.Acute GVHD occurred in 5 cases,accounting for 38.5％.Chronic GVHD occurred in 4 cases of 10 patients could be assessed,accounting for 40.0％.Severe GVHD more than Ⅱ degree did not happen.1-39 months (median time 11 months)of follow-up revealed the overall survival rate of 76.9％(10/13),disease-free survival of 61.5％ (8/13).The causes for death were relapse in all.[Conclusion]The conditioning regimen with Bu+Flu has low toxicity,well tolerance and better effect.