Natural killer (NK) cells are key members of the innate immune system.The capability of NK cells to kill hematological tumor cells mainly depends on the synthesis of stimulatory and inhibitory signals on the cells surface.In recent years,allogeneic haplo-identical NK cells have shown positive effect of hematologic tumor in hematologic stem cell transplantation and adoptive immunotherapy,and the natural killer cell-based immunotherapy would be applied in clinic.