Abstract: Objective 　To observe the variations of Caspase-3 and Caspase-9 activities in the process of simvastatin2induced apoptosis in K562 cells. Methods 　K562 cells were exposed to different concent rations of simvastatin, cell morphological analysis and flow cytomet ry were performed to confirm cell apoptosis. Colorimet ric method was used to measure Caspase-3 and Caspase-9 activities. Results 　K562 cells could be induced to undergo apoptosis af ter 5, 10, 20μmol/ L simvastatin t reatment for 48h, and the apoptotic rate was (4. 00 ±0. 13) %, (6. 24 ±0. 18) % and (9. 41 ±0. 22) % respectively, compared with the control group, it was significantly higher ( P < 0. 01) . At 72h, K562 cells were apoptotic with a rate of (7. 62 ±0. 21) %, (12. 41 ±0. 32) % and (19. 08 ±0. 26) % respectively, compared with the cont rol group, it was markedly higher ( P < 0. 01) . Furthermore, Caspase23 and Caspase29 activity in K562 cells elevated remarkably af ter 10, 20μmol/ L simvastatin t reatment for 48h and 72h, compared with the cont rol group, it was markedly higher ( P < 0. 01) . Conclusion 　K562 cells can be induced to undergo apoptosis by simvastatin, the underlying mechanism might be related to upregulation of Caspase-9 activity which subsequently t ransforms Caspase-3 into it s active form.