Allogeneic hematopoietic stem cell transplantation (allo-HSCT) in the treatment of leukemia patients can improve overall survival and disease-free survival, and reduce relapse. Although the allo-HSCT is more widely used in the treatment of leukemia, but the graft-versus-host disease (GVHD) and cytomegalovirus (CMV) infections are the common complications, and are the major cause of mortality for patients following allo-HSCT. Previous studies showed that there might be a mutual promotive relationship between GVHD and CMV infection, but the clear relationship remained to be elucidated. The relationship of GVHD and CMV has been the focus of clinical research. Recently, a great progress has been made on researches of the relationship and its mechanism between GVHD and CMV infection. In this article, the relationship and its mechanism between GVHD and CMV infection after allo-HSCT are reviewed.