Objective To investigate the inhibitory effect of rhIFN-γ on human chronic myeloid leukemia cell line K562,and the impaction on the expression of CD123.Methods MTT method was used to test cell relative viability with rhIFN-γ at different concentrations.The expression of CD123 on K562 ceils was detected by flow cytometry.Results The relative inhibition of K562 cells proliferation was hampered when the cells were treated with rhIFN-γ for 72 h at the concentration of 5 x 10P ～ 108 U/L,respectively.However,rhIFN-γ at 2 x 105 U/L was benefit to K562 cells proliferation.After treatment with rhIFN-γ at 0,2 x 105 U/L and 107 U/L,the percentages of CD123 expression on K562 cells were (4.10 ± 1.46) ％,(7.2 ± 2.50) ％ as well as (21.6 ± 1.17) ％,respectively.Compared with the control group,107 U/L rhIFN-γ significantly increased the expression of CD123 on K562 cells (P＜0.05).Conclusion The effect of rhIFN-γ on the growth of K562 cells has two aspects (inhibition or proliferation),and it can increase the expression of CD 123.