Abstract: Unconventional reservoirs represented by shale oil exhibit pronounced seismic anisotropy resulting from the preferential alignment of clay minerals and micropores, which gives rise to highly complex seismic responses. Conventional inversion methods often fail to accurately characterize anisotropy parameters, which thereby limits the precise characterization and comprehensive evaluation of fractures in shale oil reservoirs. To achieve high-efficiency and high-precision characterization of shale oil reservoirs, this study replaces the isotropic component in the Rüger approximation with the exact Zoeppritz equations. This modification improves the calculation accuracy of reflection coefficients at large incidence angles and enhances the sensitivity of anisotropy parameters to the inversion equation. In addition, a localized Kalman filter technique is introduced to effectively mitigate spurious correlations associated with limited ensemble sizes. This improvement establishes a comprehensive inversion workflow, including localization-scale analysis, prior geostatistical simulation, multi-parameter iterative updating, and uncertainty quantification. Both synthetic experiments and field-data applications demonstrate that the proposed method can achieve stable and high-accuracy inversion of elastic and anisotropic parameters, even with relatively small prior ensembles. The inversion results exhibit strong consistency with geological features and well-log observations. By effectively balancing computational efficiency and noise robustness, the proposed method provides reliable geophysical support for subsequent fine-scale fracture characterization and comprehensive sweet-spot evaluation of shale oil reservoirs.