Abstract: Objective To construct Fas-targeting siRNA expressing vector,to transfect Fas-FasL sensitive Jurkat cell line and to study its anti-apoptotic effect. Methods The siRNA expression cassettes(SECs) are generated by PCR, then Jurkat cells were transfected by Fas targeting SECs. The efficient SEC was selected by comparison of Fas mRNA level using real time fluorescent quantitative PCR(FQ-PCR) and construct the psilecircle-FasSi SEC. Fas expression of Jurkat cells transfected by psilencircle-FasSi(Jurkat-FasSi) was analyzed by FQ-PCR and Western blot. Jurkat-FasSi was treated by anti-Fas mAb to induce apoptosis and apoptotic rate was detected by flow cytometry. ResultsRestriction enzyme digestion analysis and the sequence analysis confirmed that the psilecircle-FasSi was successfully constructed. FQ-PCR and Western blot results showed that Fas expression in Jurkat-FasSi cells was down-regulated. Flow cytometry analysis using Annexin/PI staining indicated that apoptosis induced by anti-Fas antibody in Jurkat-FasSi cells was significantly inhibited. Conclusion The Fas siRNA eukaryotic expression plasmid(psilencircle-FasSi) was successfully constructed. It can down-regulate Fas expression by transfected it into Jurkat cell line and inhibited Fas-FasL pathway induced apoptosis significantly through RNAi.