Abstract: By putting ~(103)Pd-stent into canine biliary duct, proliferation of the smooth muscle cell, apoptosis and changes of the related genes after irradiation of canine biliary duct by ~(103)Pd-stent are observed. The experimental dogs are randomly divided into a common-stent group and a ~(103)Pd-stent group, 6 animals each group. Pathohistology, cell apoptosis, immuno -histochemistry for BCL-2 and FAS, RT-PCR for expression of Caspase-3 gene are performed. The results show: ① The utmost intimal thickness of biliary duct in the ~(103)Pd-stent group is obviously decreased comparing with the common-stent group after 30 days, and the percentages of the largest stenosis of the biliary duct are 54.73% and 17.61% (P<0.01) respectively; The circumference and area of biliary duct lumen are obviously increased compared to those of the common-stent group (P<0.01); ②FAS and csapase-3 expressions of smooth muscle cells of biliary duct in the ~(103)Pd-stent group are obviously decreased; ③ FAS and Caspase-3 expression in the ~(103)Pd-stent group are consistent with cell apoptosis; ④ BCL-2 expression in the ~(103)Pd-stent group is negatively related to FSA and Caspase-3 expressions. It indicats that γ radiation may induce caspase-3 gene activation which to lead the apoptosis of smooth muscle cells of canine biliary duct and to inhibit proliferation of smooth muscle cells and prevent restenosis of biliary duct.