Abstract: Objective To study the immunopathology of NK cells participating in aGVHD after nonmyeloablative haploidentical bone marrow stem cell transplantation. Methods A mouse aGVHD model was established with C57BL/6 mice as its donor and CB6F1 mice as its receptor. Symptoms and signs of aGVHD were observed, chimerism and NKp46 expression were detected. Distribution of NK cells in aGVHD target organs was detected with immunofuorescence staining. Results The incidence rate of aGVHD was 80%. The chimerism was achieved in 100% receptors 15 days after transplantation. The body weight of mice was reduced and the symptoms of aGVHD mice such as fur and hunched posture developed about 25 days after transplantation. The expression level of NKp46 was lower in aGVHD mice than in aGVHD-free mice. NK cells infltrated from donors into the portal area of receptors. Conclusion NK cells participate in the pathological response of liver graft versus host disease during nonmyeloablative haploidentical bone marrow stem cell transplantation. NKp46 expression is associated with aGVHD, thus providing evidence for the diagnosis of aGVHD.