Background: Bismuth Polyurethane composite is a novel shield for breast protection while saving image quality in chest CT. Bismuth different concentrations used for constructing polymer composites breast shields in this study. Materials and Methods: Bismuth with particle size <150 micrometer used in bismuth polyurethane composite (BPC) with a ratio of 10%, 15% and 1.1, 2.2 mm thicknesses. The BPC was examined on the female chest phantom (skin and fourth layers), 120 kV and 80 mA selected as an exposure factors in chest CT. The dose reduction was recorded by TLD and the image quality was evaluated quantitatively and quantitatively. Results: Using BPC shields 10% and 15% (2.2 mm) induced to breast dose reduction to 69.1% and 77.5% for skin layer and 44.7% and 52.8% for fourth layer, respectively.  The image noise Increasing in BPC for breast and mediastinum areas were 9.43% (P=0.347) and 15.44% (P=0.386), respectively. Conclusion: Application of Bismuth with different weight ratios in polyurethane composite was useful shield for radiation dose reduction of the breast in chest CT.