Objective To observe the effect of RNAi targeting Livin gene on biology characteristics such as apoptosis and proliferation in human prostate cancer cells.Methods siRNA expression vector targeting Livin gene was constructed and transfected into human prostate cancer cell line PC3.The expressions of Livin mRNA and protein were detected by real-time PCR and Western-blot,cell apoptosis and cell cycle were assayed by flow cytometry,proliferation and colony formation were detected by MTT and colony formation assay,and the tumor growth in vivo was observed in nude mice.Results After transfection,downregulation of Livin mRNA and protein expression in PC3 cells was observed (P＜0.01).Compared with the control group,the proliferation of cancer cells was inhibited significantly (P＜0.01) and the apoptotic ratio was (26.5±3.3) ％ (P＜0.01).The Caspase3 activity increased obviously (P＜0.05),and the experimental group showed a decreased colony formation rate (P＜0.01).The tumor volume of xenografts in nude mouse in experimental and control group was (1.79± 0.07) and (4.40 ± 0.06) cm3 respectively (P ＜ 0.01).Conclusions The siRNA recombinant expression vector targeting Livin gene was constructed and can knockdown the expression of Livin mRNA and protein.It can inhibit PC3 cell proliferation,induce apoptosis and inhibit tumor growth in vivo.