Stem cells refer to hematopoietic stem cells, and the detailed steps of hematopoietic stem cell transplantation are generally preoperative preparation, infusion of stem cells, treatment of bone marrow suppression period, and monitoring during observation period. 1. Preoperative preparation: hematopoietic stem cell transplantation should be chosen to be performed when the patient is in good condition. Therefore, before transplantation, both donors and patients need to undergo general physical examination, air disinfection in laminar flow ward, removal of infected lesions and other operations. The patient should enter the cabin about 1 week before the transfusion of hematopoietic stem cells, and before entering the cabin, the hair of the whole body should be removed, and the whole body medicated bath and whole body disinfection should be carried out. 2. Transfusion of stem cells: after entering the laminar flow cabin, patients should firstly undergo chemotherapy (fludarabine, leucovorin) for about 3 days to empty the bone marrow, and then return to the normal hematopoietic stem cells of the donor, and the time of returning to the infused cells is generally about 2 days. 3. Myelosuppressive period: after the transfusion, the patient enters the myelosuppressive period, during which attention should be paid to the prevention of infection, and supportive treatment such as blood transfusion can be given. 4. Observation period: during this period, patients can be transferred to general ward after hematopoietic cell function is restored, and can be discharged to recuperate after the disease is stabilized. At this time, the patient will enter the observation period, which lasts for about one year. There are other steps in stem cell transplantation, which need to be carried out under the guidance of doctors.