Abstract: Natural killer cells (NK cells) can kill target cells directly and rapidly through their intrinsic receptor recognition,serving as important immune cells for anti-tumor therapy.To considerable extent,the activation of NK cells is negatively regulated by inhibitory receptors,but these inhibitory receptors are often utilized to evade immune surveillance in the tumor microenvironment.In recent years,preclinical and clinical trials of blocking antibodies based on KIR,NKG2A,TIGIT and CD96 have shown that NK cell malfunction in tumors can be reversed to enhance anti-tumor immunity.To this end,the functional characteristics of inhibitory receptors found in human NK cells,as well as related tumor immune escape mechanisms and the progress in targeted therapy of cancer immunotherapy are summarized in this article.