Eight patients with severe aplastic anemia received unrelated cord blood transplantation at the Guangzhou First People's Hospital from June 1998 to December 2007. The patients were conditioned with decreased dosage of immunosuppressive agents of cyclophosphamide and antilymphocytic globulin. The median infused donor total nucleated cell were 5.69×10 7/kg of recipient weight, and the CD34+ cell was 4.10×105/kg of recipient weight. Methotrexate and corticoid methylprednisolone were used for prophylaxis of graft versus host disease (GVHD). The time to reach an absolute neutrophil count of 0.5×109/L ranged from 7 to 25 days (median: 17 days) and the time to reach a platelet count of 20×109/L ranged from 13 to 102 days (median: 35 days) after transplantation. DNA finger print map of 7 patients showed donor and recipient chimera. Two patients developed grade I to II acute GVHD, which was controlled. One patients developed grade II chronic GVHD, which was controlled by using methylprednisolone. Five patients had lived for 10-108 months, with no diseases. Taken together, unrelated umbilical cord blood transplantation is effective for adult patients. Partial conditioning regiment could ensure engraft of unrelated umbilical cord blood transplantation.