Abstract: Objective 　To investigate the influence of proteasome inhibitor PS-341 (Bortezomib) on apoptosis-induced cell line U266 cytoplasmic Ca²⁺ ( Ca²⁺i) . Methods 　U266 cells were exposed to different concent rations of PS-341 for 4 hours, then cells apoptosis were analyzed by fluorescence microscope and flow cytomet ry ( FCM) with Annexin V-FITC/ PI double staining, and cytoplasmic free calcium were detected on FCM throught Fluo-3/ AM loading. Results 　(1) Apoptotic cells were gradually increased with PS-341 concentrantions increased under fluorescence microscope ; (2) The appearance rates of apoptotic cells were 0. 56 %、7. 71 %、19. 84 %、31. 10 %、40. 72 % respectively on FCM and apoptotic cells rates were in dose-dependent ; (3) The mean of Ca²⁺ i were 403. 65 nmol/ L 、418. 20 nmol/ L 、378. 65 nmol/ L 、356. 36 nmol/ L 、349. 21 nmol/ L, respectively, treated with PS-341. (4) PS-341 induced U266 cells apoptosis following Ca²⁺i change, and was related to the down regulation of Ca²⁺i when the dose exceeded 50nmol/ L. Conclusion 　PS-341 induced U266 cells apoptosis in dose-dependent fashion ;when concentration excessed 50 nmol/ L PS-341 down regulated Ca²⁺i, and to exert its induce apoptosis activity by these pathways.