Objective To evalute the safty and efficiency of allogeneic hematopoietic stem cell transplantation (allo- HSCT) in pri-mary myeloid sarcoma (MS). Methods The clinical manifestations, diagnosis, and treatment of 4 cases with primary MS treated with al-lo- HSCT were retrospectively analyzed. Results All of the 4 patients presented with extramedullary tumors as first symptom. Pathologi-cal biopsies were performed. Immuno- histological analysis showed that myeloperoxidase (MPO) were positive in all 4 cases, while CD68, lysozyme and CD34 were positive in some cases. After the chemotherapy, myeloablative allo- HSCT were administrated in these 4 patients. At present, 1 patient died because of the progression of the disease, while 3 patients survived. Conclusion Allo- HSCT in treating primary MS is safe, and can bring patients better disease- free survival (DFS).