Abstract： Objective To study the effect of thalidomide and arsenic trioxide on the proliferation and apoptosis effect in human myelodysplastic syndrome cell line MUTZ-1 and explore its possible mechanism.Methods MUTZ-1 cells were cultured with different concentration of thalidomide alone, arsenic trioxide alone, and thalidomide plus arsenic trioxide for 48 h. The cell proliferation was analyzed by CCK-8 test, and cell apoptosis was analyzed by flow cytometry. The expression of Bmi-1 was analyzed by semi-quantitative RT-PCR. Results Thalidomide alone had no significant inhibition on growth of MUTZ-1 cells (P >0.05).Arsenic trioxide alone had obviously inhibited the cell proliferation (P <0.05). While thalidomide plus arsenic trioxide group had the great inhibition effect(CDI <0.7), and reveal was that two drugs had synergism effect on inhibiting the MUTZ-1 cells. Arsenic trioxide group of apoptosis rate was increased with higher concentrations of drug, a dose-dependent (r = 0.627, P <0.05), thalidomide in the rate of apoptosis with no increase in drug concentration significantly (r= 0.313, P> 0.05), and the combined group with the drug also increased the concentration of expression (P <0.05). In arsenic trioxide group the expression of Bmi-1 / β-actin declined with the increased concentration, a dose-dependent (r =-0.912, P<0.05), thalidomide group Bmi-1 / β-actin with the increased concentration of no significant decline (r =-0.594, P >0.05), the combined group Bmi-1 inhibition was significantly higher than arsenic trioxide, thalidomide in a separate drug group (CDI <0.7).Conclusion Thalidomide group had no significant growth inhibition. Arsenic trioxide on MUTZ-1 cells significantly inhibited the growth and increased in the combined group significantly.