Abstract： Background Internal metallic stents have been widely used in clinical practice, but a high postoperative restenosis rate limits its application. The purpose of this study was to determine the effect of intrabiliary radiation on muscle formation and biliary duct remodeling after biliary duct balloon injury in dogs. Methods Twenty male dogs (15-20 kg) were randomly divided into treatment group (n=10) and control group (n=10). Balloon overstretching injury was induced using a balloon catheter placed across the biliary duct. Subsequently, a 103Pd radioactive stent was positioned at the target site in each animal in the treatment group, providing the injured biliary duct with a radiation dose of 12.58×107 Bq. Dogs in the control group received Ni-Ti stents. All the dogs were killed one month after initial injury. The injured sections were dissected free from the dogs, and were processed for histological and morphological study. Cross-sections were stained with hematoxylin-eosin, Masson's trichrome, and Verhoef-van Giesen. Muscle formation area and lumen area were determined using a computer-assisted image analysis system. Results Compared with the control group, 103Pd radioactive stents significantly reduced muscle formation area (78.3%, P＜0.01), and percentage area of stenosis [control stents: (60.0±21.6)%, 103Pd radioactive stents: (31.6±9.5)%]. In addition, in the treatment group, the biliary duct lumen area was significantly larger than that in the control group (P＜0.01). Conclusions 103Pd radioactive stents providing a radioactive dose of 12.58×107 Bq are effective in reducing muscle formation and biliary duct remodeling after balloon overstretching injury.