It usually takes about 3 months after a leukemia transplant to pass the danger period, but there are variations depending on the type of transplant and the individual’s constitution. Leukemia is a malignant disease of the hematopoietic system and bone marrow transplantation is its only cure. Bone marrow transplantation is a risky procedure, from the pretreatment chemotherapy phase to the transplantation of stem cells, then to the exit from the sterile compartment, and finally to the recovery of hematopoietic function, all of which are risky and usually take about 3 months. After a bone marrow transplant, the recipient’s body is generally less resistant and highly susceptible to infections and other complications, and the recovery time may be shorter for individuals with better health. In addition, some people may experience rejection, especially in allogeneic bone marrow transplants, which increases the risk of rejection. After leukemia bone marrow transplantation, one should standardize the treatment under the guidance of the doctor and be confident in order to get through the dangerous period as soon as possible.