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. In autologous hematopoietic stem cell transplantation, the hematopoietic stem cells are derived from oneself, so graft rejection and graft-versus-host disease will not occur, there are few complications of transplantation, and there is no restriction of donor source, the mortality rate related to transplantation is low, and the quality of life after transplantation is good, but the recurrence rate is high because of the lack of anti-tumor effect of graft and residual tumor cells may be mixed in the graft. Allogeneic hematopoietic stem cell transplantation has a low relapse rate and a high long-term disease-free survival rate (which can also be interpreted as a cure rate) because the hematopoietic stem cells are derived from normal donors without tumor cell contamination, and the graft has an immune anti-tumor effect, which has a wide range of indications and is even the only cure for certain diseases. Patients require long-term immunosuppression, and long-term survivors may have a poor quality of life.