Abstract: Objective: To study the effect of specific inhibition of high mobility group Box1 gene expression bysmall interfering RNAs (siRNA) on the proliferation of human prostate carcinoma cell line PC3. Methods: We construct-ed and identified an eukaryotic expression vector carrying human Pgenesil1/HMGB1siRNA. The vector was transfectedinto PC3 cells by Lipofectamine 2000 and the stable clones were selected with G418. The HMGB1 expression in PC3cells was detected by RTPCR and Western blot before and after transfection. Flow cytometry was employed to detect thepercentage of cells in each phase of the cell cycle. The in vitro proliferation activity was examined by MTT analysis. Re-sults: The recombinant plasmid Pgenesil1/HMGB1siRNA was successfully constructed. The introduction of Pgenesil1/HMGB1siRNA efficiently and specifically inhibited the expression of the HMGB1 gene according to the results of RT-PCR and Western blot, with a significant difference between the siRNAtransfected group and the group without siRNAtransfection (P<0.05). Cell proliferation in the Pgenesil1/HMGB1siRNA group was significantly inhibited (P<0.05). Conclusion: siRNA targeting HMGB1 mRNA can specifically suppress HMGB1 gene expression and can effectively inhibitthe proliferation of PC3 cells, providing a potential new method for cancer biotherapy.