This study was aimed to explore the killing effect of PBMNC induced by IL-23 alone or combined with IL-2 on K562 cells and its mechanism. The PBMNC were induced in vitro by IL-23 (50 ng/ml) alone or IL-23 combined with IL-2 (100 U/ml) for 72 h, and then were co-cultured with leukemia cell line K562. The CCK-8 method was used to detect the effect of PBMNC induced at different times on K562 cells, the ELISA was performed for detecting IFN-γ level in culture supernatant, and the perforin and granzymes B were detected by RQ-PCR. The results showed that the killing effect of PBMNC induced by IL-23 alone or IL-23 combined with IL-2 on K562 cells was observed, and obviously enhanced with prolonging of time, moreover, there was statistical difference among different time points (P < 0.05). The IFN-γ level in supernatant of PBMNC cultured with cytokines significantly increased, and the IFN-γ levels in group of IL-23 combined with IL-2 were higher than that in other groups (P < 0.05). The mRNA expressions level of perforin and granzymes B of the expanded PBMNC in groups cultured with cytokines were higher than that in control group (P < 0.05), and the mRNA expressions of perforin and granzymes B in group of IL-23 combined with IL-2 were significantly higher than that in others (P < 0.05). It is concluded that IL-23 can promote the killing effect of PBMNC on K562 cells. The combination of IL-2 with IL-23 displays synergic effect and a time-dependent manner. IL-23 also enhances the expression of IFN-γ, perforin and granzyme B in PBMNC. Its combination with IL-2 displays synergistic effect, suggesting that the anti-leukemic activity of IL-23 may be realized through inducing PBMNC to express IFN-γ, perforin and granzyme B.