Abstract: Objective To analyze the safety and efficacy of fludarabine and busulfan（FB） as a reduced intensity myeloablative conditioning regimen for allogeneic stem cell transplantation in elderly or other hematologic malignancies patients who were not well tolerance to standard myeloablative conditioning regimen. Methods Data of 14 patients who underwent allogeneic stem cell transplantation with FB conditioning regimen from August of 2009 in the Hematology Department of PLA General Hospital were retrospectively studied. Results Fourteen patients,12 older than 50 years old and 3 patients ever received transplantation with myeloablative conditioning regimen,tolerated the allogeneic stem cell transplantation with FB conditioning regimen well.Patients achieved myeloid and platelet engraftment at a median of 13（10-16） days and 17（13-28） days,respectively.All patients achieved full donor chimerism at 28 days after transplantation.After a 9.5（3-22.5） months follow-up,the incidence of acute graft-versus-host disease（GVHD）,the chronic GVHD,the relapse and the 2-years overall survival were 35.6%,33.3%,14.3% and（54.4±14）%,respectively. Conclusion Conditioning regimen with FB were safe and efficient for hematologic malignant patients who were not eligible for standard transplantation,but the management of immunosuppression drugs and infection should be taken into consideration.