This study was purposed to investigate the effect of xbp-1 gene silencing on bortezomib-induced apoptosis in multiple myeloma cell line NCI-H929 (H929). After xbp-1 gene expression was interfered by small hairpin RNA, the cell apoptosis was assayed by flow cytometry with Annexin V-FITC/PI staining, and the expression level of XBP-1 protein was detected by Western blot. The results showed that XBP-1 protein level of H929 cells was inhibited effectively by the PLL3.7 lentiviral vector mediated expression xbp-1 shRNA. The apoptosis rate was significantly higher in xbp-1 shRNA-expressing cells than in untreated control group [(10.13±0.61)% vs (2.5±0.2)%, p<0.05]. After treatment with bortezomib, the apoptosis rate of XBP-1 protein functionally deficient H929 cells was significantly higher than those in vector control group [(45.07±1)% vs (19.53±0.8)%, p<0.05]. It is concluded that xbp-1 gene silencing can significantly enhance the pro-apoptotic activity of bortezomib in multiple myeloma cells.