There is a significant difference between the terahertz frequency and low frequency in the polarization scattering characteristics of targets. Taking dihedral angle as the research object, the influence of different surface roughness on the identification of target scattering structure and the integrity of profile is studied. Firstly, the rough model is geometrically constructed based on the linear filtering method. Then, the component interpretation is performed on the polarization image by Pauli polarization decomposition, and the integrity of target contour in radar image is quantitatively analyzed. Finally, the electromagnetic simulation results prove that the even component of dihedral angle decreases and the odd component increases with the increase of roughness, and the integrity of target profile is higher in radar image. Results show that the fusion of polarization interpretation and optical interpretation is an important approach for target recognition at terahertz frequencies.