Objective To investigate the effect of FCGR3A polymorphisms on NK cell function. Methods Peripheral blood samples from can?cer patients were collected and FCGR3A polymorphisms were confirmed by PCR. In vitro proliferation rates,ADCC activity,and expression of NK cell activating receptors were compared under trastumab stimulation. Results This study showed that the wild?type FCGR3A exhibited a higher affinity to trastumab along with better NK cell proliferation and ADCC activity than the mutant type. Compared to the patients with wild?type FC?GR3A,the proliferation rates of NK cells in patients with the mutant type were reduced by approximately 8?fold. In addition,the expression of NK cell activating receptors in patients with wild?type FCGR3A was higher than in patients with the mutant type. Conclusion Mutations in FC?GR3Areduce NK cell function,causing a poor reaction to monoclonal antibody.