Abstract: From the view of intrinsic mechanism of NK cytotoxicity, the kinetic model of cytotoxic reaction and tlse singly cell assay were used to observc and analyze the effecting link of T4 on NK activity. The results showed that the dosage enhancing NK activity could increase the frequency(%E) of killer cell in the splenocyte population, axed the rate constant of lysis(K2) so that the maximum (Vmax) of NK cell was raised.