Abstract Natural killer cells (NK) are important immune cells that recognize and eliminate virus-infected cells and tumor cells. NK cells play a crucial role in anti-tumor immunity by modulating the immune response through a variety of cytotoxic mechanisms and cytokine production. This article reviews the development and classification of NK cells, the mechanism of action, and the application of NK cell-based immunotherapy in tumor immunity, and clarifies the principle, status quo and development trend of NK cell-based anti-tumor immunotherapy, in order to provide ideas for the future research and development of NK cells.