Abstract: Objective 　To investigate effect s of nm23-H1 overexpression on cell cycle and differentiation of HL60 cells. Methods 　Recombinant expression vector pEGFP-N1-nm23 H1 was constructed and transfected into HL60 cells with the aid of liposome in a transient way. Expression of fusion protein nm23-H1-EGFP was detected under the fluorescence microscope. Flow cytomet ry was adopted to analyze cell cycle. Differentiation rate of the DMSO-induced HL60 cells was tested by NBT reduction assay. Results 　Expression level of recombinant plasmid pEGFP-N1-nm23 H1 in HL60 cells reached a peak at 48h after transfection. Meanwhile, proportion of S-phase cells increased dramatically and HL60 cells became less sensitive to differentiation inducer DMSO. Conclusion 　Overexpression of nm23-H1 gene could stimulate proliferation but inhibit differentiation of HL60 cells. nm23-H1 gene might be a potential target of leukemia treatment .