The aim of this study was to investigate the effects of Celecoxib on the proliferation, apoptosis, cell cycle and CD117 expression of K562 cells, and to explore its synergistic effect with IFN-alpha. K562 cells were treated with IFN-alpha, Celecoxib and combination of Celecoxib with IFN-alpha at different concentrations. The inhibitory effect of Celecoxib and IFN-alpha on cell proliferation was detected with MTT assay, the cell apoptosis, cell cycle and CD117 expression were determined by morphology observation and flow cytometry. The results showed that the Celecoxib inhibited proliferation of K562 cells in concentration-dependent manner (r=-0.91). After culture of K562 cells for 72 hours, the rates of K562 cell proliferation in control group, IFN-alpha group, Celecoxib group and IFN-alpha-combined Celecoxib group were (96.1+/-0.5)%, (90.2+/-0.4)%, (57.2+/-0.9)% and (21.9+/-0.3)% respectively. The cell apoptosis rates in 4 groups were (5.5+/-0.8)%, (6.3+/-0.6)%, (26.4+/-3.9)% and (57.3+/-4.5)% respectively. The CD117 expression rates in 4 groups were 54.7%, 10.5%, 36.3% and 7.3% respectively. Combination of Celecoxib with IFN-alpha might block K562 cells in G0/G1 phase. In conclusion, Celecoxib and IFN-alpha both may inhibit K562 cell proliferation, induce apoptosis, reduce CD117 expression and produce G0/G1 phase block to various degree and the two drugs have a synergistic effect.