Hematopoietic stem cell transplantation (bone marrow transplantation), which is a complex series of works. It is a treatment for the eradication of many stubborn, hereditary, and tumor diseases under full environmental protection in a sterile laminar flow ward. It is based on killing/destroying tumor cells or immune functions as much as possible, and transfusing patients with hematopoietic stem cells (their own or others’), the imported stem cells will re-differentiate and develop to grow healthy hematopoietic cells and immune functions, and restore health and welcome the future through new hematopoietic/immune functions! The new hematopoietic/immune function restores health and welcomes the future! Therefore, it mainly includes several aspects: indications for transplantation, pre-transplantation preparation (HLA matching, donor stem cell mobilization, stem cell collection and storage), pre-treatment of patients before transplantation, prevention of graft-versus-host disease, stem cell infusion, hematopoietic and immune recovery, and post-transplantation follow-up (review of the original disease and management of complications). Indications for transplantation: hematologic neoplastic diseases such as acute leukemia, lymphoma, myeloma, myelodysplastic syndrome (MDS) and myeloproliferative diseases; genetic diseases: thalassemia major, etc.; bone marrow failure diseases: aplastic anemia major, etc.; hematopoietic stem cell deficiency diseases: paroxysmal sleep hemoglobinuria (PNH), etc.; connective tissue diseases: refractory systemic lupus erythematosus, rheumatoid arthritis, etc. …… Bone marrow transplantation is divided into autologous and allogeneic transplantation according to the source of bone marrow, and now we will talk about autologous transplantation for the time being. Autologous transplantation, as the name implies, is the extraction of one’s own hematopoietic stem cells (collected after mobilization) and then transfused back to oneself (transfusion). Autologous transplantation does not require HLA matching because there is no rejection problem. It is generally indicated for the treatment of myeloma, lymphoma, low- and intermediate-risk acute myeloid leukemia and some connective tissue diseases, and of course for the consolidation of other neoplastic diseases without allogeneic bone marrow sources. It has two key techniques: stem cell mobilization and pre-transplantation pretreatment. Since autologous transplantation has no graft antitumor effect, its success is predicated on whether the primary disease is well controlled or not, and the key lies in whether the pretreatment can further clear the tumor cells to further reduce the body’s tumor load and reduce the chance of recurrence, of course, the treatment process needs sufficient stem cells to escort. Stem cell mobilization: Patients who are selected and agree to undergo bone marrow transplantation should undergo different programs of induction remission therapy and consolidation therapy according to different diseases, and after consolidation therapy, they should enter the stem cell mobilization for transplantation preparation. Mobilization protocols are divided into two categories: original consolidation therapy protocols and classical mobilization protocols. The original consolidation regimen mobilization is combined with G-CSF mobilization when myelosuppression is the most severe after consolidation chemotherapy, usually G-CSF is used 5-7 days after chemotherapy, and stem cells are collected during the neutrophil recovery period 10-14 days after chemotherapy; the general mobilization regimen includes the classical high-dose CTX/VP-16 combined with G-CSF mobilization (the specific timing of collection depends on the number of routine blood leukocytes, single nucleated cells (the exact timing of collection depends on blood count, percentage of mononuclear cells and CD34+ cell content). After collection, the specimens are sent for individual nuclei count and CD34+ cell count to ensure the number of stem cells (generally, the individual nuclei count is greater than 3-4*10e8/kg (affected body weight) and the CD34+ cell count is greater than 3-4*10e6/kg (affected body weight)), and the specimens are cryopreserved after collection (plasma and red blood cells should be removed from bone marrow; plasma should be removed from peripheral blood to reduce volume. (Note that the cells are washed after thawing to remove dimethyl sulfoxide). Second, pretreatment protocols, commonly used are BU/CY, CBV, BEAM, high-dose Marfalan, CTX, etc. Different transplant centers perform different protocol options for different diseases.