Abstract: Resonant ultrasound spectroscopy method is a high-precision method for identifying the full elastic coefficients of materials by using the resonant frequencies. The method is widely used in the calculation of the elasticity of solid materials with high Q value. However, for materials with higher viscoelastic damping, the application of this method meets certain difficulties due to the difficulty in identifying the resonant modes with the overlapped resonant spectrum. This study established a Bayesian formulation of elastic coefficients, with the global search ability of Particle Swarm Optimization (PSO), to find the maximum posterior probability density point of elasticity, and finally realized the identification of elasticity of materials. The elastic coefficients of a simulated cortical bone specimen were measured. Compared with the traditional method, the PSO-based resonant ultrasound spectroscopy is not sensitive to the initial guessing value of the elastic coefficients and can be used for the measurement of the elastic properties of high damping materials.