For a long time, there has been a debate on the merits of cord blood stem cell transplantation, autologous bone marrow stem cell transplantation and peripheral blood stem cell transplantation. Cord blood is rich in stem cells and needs to be separated by biotechnological means. There are strict screening standards for mothers and fetuses who provide cord blood, and national standards have been formed for the collection, separation and freezing of cord blood. 2.Biological characteristics of cord blood stem cells: Cord blood contains a large number of hematopoietic stem cells and abundant mesenchymal stem cells, which are comparable to the number in human bone marrow, and cord blood stem cells are more primitive and have stronger differentiation ability, which not only support the hematopoietic system but also differentiate to tissues of mesodermal and ectodermal origin. 3.What are the advantages of cord blood stem cells compared with autologous bone marrow stem cells: ① Cord blood is abundant, convenient and safe to collect, there is no harm or damage to the mother and the newborn, and it is easy to collect and preserve; however, bone marrow collection and the use of cytokines to mobilize peripheral blood to obtain stem cells can bring certain risks to the donor or the patient himself. ②Cord blood has a strong proliferation and differentiation ability. The stem cells in cord blood are not fully differentiated and mature, so they are more primitive and have a stronger proliferation and differentiation ability than the stem cells in adult bone marrow. (3) Immune cells in cord blood are more naive, immature in immune function, and in a state of silence. They are less immunogenic than bone marrow-derived stem cells, and as a type of immune-exempt cells, they are not subject to strict pairing, and allogeneic transplantation is not subject to immune rejection. Cord blood stem cells are relatively pure, and the chance of infection and transmission of latent viruses and pathogenic microorganisms in cord blood is relatively low, while bone marrow stem cells, especially autologous bone marrow stem cells from hepatitis B patients, have defects in their own proliferation ability. ⑤ Cord blood stem cells are easy to preserve and transport.