Objective：To investigate the effect of bifidobacterium infantis（BI）-mediated herpes simplex virus thymidine kinase（HSV-TK）/ganciclovir（GCV） suicide gene therapy system on cell apoptosis of prostate cancer PC-3 cell xenografts in nude mice. Methods：The prostate cancer model was established by subcutaneous injection of human prostate cancer cell line PC-3 into nude mice. The model mice were randomly divided into 4 groups，which were treated by intraperitoneal injection of GCV in combination with tail vein injection of BI carrying recombinant plasmid BI-pGEX-TK（recombinant plasmid group），BI carrying empty plasmid BI-pGEX-5x-1（empty plasmid group），BI（BI group） and normal saline（normal saline group）. After 4 weeks of treatment，tumor weights and nude mice weights were recorded. The apoptosis of tumor was detected by TUNEL assay. The expression of Fas，FAP-1，casepase3 and casepase8 were determined by real-time qPCR and Western blot，respectively. Results：After treatment，comparing with those of empty plasmid group，BI group and normal saline group，the nude mice weights in recombinant plasmid group increased（F=12.952，P=0.000），the tumor weights decreased（F=7.795，P=0.000）. The apoptosis index of recombinant plasmid group was obviously higher than that of the other three groups（F=45.895，P=0.000）. Comparing with the other three groups，the mRNA expression of Fas（F=70.077，P=0.000），casepase3（F=70.611，P=0.000） and casepase8（F=73.781，P=0.000） in recombinant plasmid group increased，but the mRNA expression of FAP-1（F=46.880，P=0.000） decreased. Protein expression of Fas（F=664.116，P=0.000），casepase3 F=203.090，P=0.000） and casepase8（F=654.354，P=0.000） in recombinant plasmid group increased，but the expression of FAP-1 protein（F=318.989，P=0.000） decreased. Conclusion：The BI-mediated HSV-TK/GCV suicide gene therapy system can inhibit nude mice prostate cancer progression effectively，probably through affecting Fas mediated apoptosis signaling pathways，inducing to nude mice prostate cancer cells apoptosis and playing a role in tumor suppression.