Chronic lymphocytic leukemia(CLL) is an indolent lymphoproliferative disorder with great clinical heterogeneity. The immunochemotherapeutic regimens have improved the outcome of majority of the patients. Nonetheless, in some patients, the disease progresses shortly after the immunochemotherapy, while in others, it becomes refractory and drug resistant. Allogeneic hematopoietic stem cell transplantation(allo-SCT) potentially cures CLL due to the graft versus CLL effect. It has been wildly accepted that allo-SCT is a good option for young CLL patients with high risk factors, including purine analogue resistance, early relapse after purine analogue-based treatment, and 17p deletion and TP53 mutation. Reduced-intensity conditioning regimens effectively decrease the treatment-related mortality.