Abstract: To address the challenges posed by the complex microstructure and modeling difficulties of 8 wt.% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) fabricated via electron beam physical vapor deposition (EB-PVD), a three-dimensional columnar microstructure was numerically reconstructed using the Quartet Structure Generation Set (QSGS). Considering the critical role of TBCs in the thermal protection of high-temperature components, the Asymptotic Homogenization Method (AHM) was employed to evaluate their effective mechanical properties. Based on multiscale asymptotic expansion, this method enables the derivation of macroscopic stiffness tensors from periodic microstructures by solving characteristic displacement fields. The influences of microstructural features on the effective Young’s modulus, shear modulus, and Poisson’s ratio were investigated by systematically adjusting parameters such as porosity, aspect ratio, and pore size. Results indicate that increasing porosity significantly reduces stiffness and intensifies anisotropy. A higher pore aspect ratio enhances stiffness along the columnar direction while weakening transverse coupling. Reducing pore size improves stiffness, greater microstructural uniformity, and enhanced isotropy. These findings provide theoretical support and numerical reference for the multiscale modeling and structural optimization of thermal barrier coating systems.