Friction material properties critically impact brake squeal simulation outcomes due to their nonlinear and transversely isotropic behaviors, which vary with load type and direction. To improve the reliability of brake squeal predictions, this study introduces the Transversely-isotropic Elastic Constants Optimization (TECO) method, a novel multi-dimensional constrained optimization framework for refining the elastic constants and damping ratio of friction materials. By integrating experimental testing, finite element analysis (FEA), and an advanced optimization technique - Gradient Response Surface Algorithm (GRA), the TECO method minimizes discrepancies between simulated and experimental data, ensuring accurate characterization of elastic properties. The TECO method offers significant advantages, including flexibility and robustness, making it an effective alternative to ultrasonic measurements and traditional optimization techniques, especially for anisotropic friction lining materials. Unlike existing approaches, TECO imposes no restrictions on the number of defined modes, allowing accurate characterization with fewer input data points. Its iterative process ensures strong correlation between experimental and simulated results while preserving essential modal attributes, such as natural frequencies and mode shapes. Focused on drum brake squeal prediction, the TECO method enhances complex eigenvalue analysis (CEA) by incorporating friction material properties measured under actual squeal loading conditions. This approach yields highly correlated NVH simulation models at the component level, providing a reliable framework for brake squeal analysis and design. By advancing the predictive accuracy of brake squeal simulations, the TECO method offers a versatile and effective solution for characterizing friction material properties, contributing significantly to noise, vibration, and harshness (NVH) optimization strategies in braking systems.