This paper provides a theoretical model for studying typical airport ground materials’ polarization characteristics which is required for the development of polarization imaging instruments. First, serious shadow masking effects were analyzed based on the P-G model. These effects occur when light is incident at a large angle. Then, the shadow masking function was optimized using the spherical trigonometry formula. This optimization equates the specular reflection point to a three-dimensional sphere. Due to the unique dispersion characteristics of different targets, a new bidirectional polarization distribution function (BPDF) model was introduced to replace the traditional BRDF parameter affected by wavelength and body scattering. The new BPDF model integrates diffuse reflection and body scattering. In the experimental stage, the accuracy of the line polarization degree was calibrated. The line polarization degree of typical airport ground material was fitted with model parameters. This fitting was based on the dynamic TS algorithm through multi-angle BRDF experiments. The fitting model's six parameters were used to obtain the root mean square roughness parameter. This process verified the validity of the modified BPDF model. In the simulation stage, the root mean square error (RMSE) was used as the accuracy index. The modified BPDF model, control model, and experimental results were compared to analyze the effects of detection, azimuth, and incidence angles on polarization characteristics. The accuracies of the four experimental targets improved by 4.39%, 4.00%, 4.17%, and 5.26% compared with the control model. The RMSE was less than 0.05 for large detection angles. This allows the modified model to study polarization characteristics of rough materials like airport ground targets. Finally, the effect of fitting parameters on polarization characteristics was simulated. Results show that line polarization is positively related to the refractive index and inversely related to the surface roughness. The accuracy of the modified BPDF model is thus proved. This provides ideas for studying polarization characteristics of airport ground targets.