Hematopoietic stem cell transplantation is a treatment in which patients first receive mega-dose radiotherapy or chemotherapy (usually lethal dose of radiotherapy or chemotherapy), sometimes combined with other immunosuppressive drugs, to remove tumor cells and abnormal clonal cells from the body, and then transfuse back hematopoietic stem cells harvested from themselves or others to re-establish normal hematopoietic and immune functions. Therefore, scientifically speaking, hematopoietic stem cell transplantation is a medical treatment, not a surgery. When media reports on hematopoietic stem cell transplantation, the word ‘surgery’ is always mentioned, probably to set the mood and attract readers’ attention, but this will easily mislead the public about hematopoietic stem cell transplantation. There are various ways to classify hematopoietic stem cell transplantation. The hematopoietic stem cells come from oneself or others, which become autologous hematopoietic stem cell transplantation and allogeneic (also known as allogeneic) hematopoietic stem cell transplantation, where allogeneic hematopoietic stem cell transplantation is divided into blood-related donor hematopoietic stem cell transplantation and bloodless donor hematopoietic stem cell transplantation (i.e. unrelated transplantation) according to the type of graft; peripheral blood hematopoietic stem cell transplantation, bone marrow transplantation and cord blood hematopoietic stem cell transplantation according to the type of graft. Bone marrow transplantation and cord blood HSCT. HSCT can treat many hematologic diseases, including: hematologic malignancies, such as acute leukemia, chronic granulocytic leukemia, lymphoma, multiple myeloma, myelodysplastic syndrome, etc., and certain hematologic non-malignant tumors, such as severe aplastic anemia, thalassemia Patients with lymphoma, multiple myeloma and certain acute leukemias with a low risk level are suitable for autologous hematopoietic stem cell transplantation, while patients with acute leukemia, chronic granulocytic leukemia, myelodysplastic syndrome, severe aplastic anemia, and thalassemia with a moderate or high risk level are suitable for allogeneic hematopoietic stem cell transplantation. It should be emphasized that chronic granulocytic leukemia and myelodysplastic syndrome are hematopoietic malignancies caused by abnormal hematopoietic stem cells. Although there are many advanced drugs available to treat these patients at the genetic level, allogeneic hematopoietic stem cell transplantation is still the only treatment to cure these diseases.