This study was purposed to explore the changes in biological functions of human peripheral blood derived NK Cells after ex vivo expansion with different combinations of interleukin IL2 and/or IL12, IL15. According to different combination of cytokines, cultured NK cells were divided into 4 groups: group IL2, group IL2 + IL12, group IL2 + IL15 and group IL2 + IL15 + IL12. The group in which NK cells were cultured without cytokines was used as control. The cytotoxicity of cultured NK cells to target K562 cells was determined by using cell counting kit-8; the level of IFN-gamma in supernatants of NK cell culture was detected by ELISA; the perforin and granzyme B mRNA expressions were assayed by competitive quantitative RT-PCR. The results showed that the cytotoxicity of expanded NK cells in groups cultured with cytokines at different E:T ratio was significantly higher than that in group without cytokines (p < 0.01), although the cytotoxicity of NK cells in IL2 + IL15 + IL12 group seem to be slightly higher than that in IL2 + IL15 group, but there was no statistic difference (p > 0.05). The IFN-gamma levels in the supernatants of NK cell culture in the presence of cytokines significantly increased, and the IFN-gamma levels in IL2 + IL15 + IL12 group and IL2 + IL12 group were significantly higher than that in others (p < 0.01). The expressions of perforin and granzyme B mRNA of expanded NK cells in groups cultured with cytokines was significantly higher than that in control group (p < 0.01), and was consistent with cytotoxicity of NK cells. It is concluded that there are differences in the functions of NK cells cultured with different cytokines. IL2 and IL15 have synergistic effect on strengthening cytotoxicity of NK cells and promoting cell expansion. However, the main function of IL12 promotes NK cells to secrete IFN-gamma, which plays a role in immunoregulation.