Abstract: Ultrasonic guided waves can characterise both the geometrical features (e.g., thickness, cross-sectional shape) and mechanical properties (e.g., bone density, Young's modulus, etc.) of cortical bone. In this paper, the correlation between osteoporosis and the mechanical parameters of cortical bone is investigated using the ultrasonic guided wave dispersion curve inversion algorithm through cortical bone simulation experiments and isolated bovine tibia experiments. The results show that the thickness, Young's modulus, and Poisson's ratio of cortical bone are accurately inverted. With the increase in cortical bone porosity, Young's modulus and Poisson's ratio exhibit a strong correlation with porosity: Young's modulus is negatively correlated, while Poisson's ratio is positively correlated. The mean coefficients of variation for Young's modulus and Poisson's ratio are −0.45 and 0.20, respectively, indicating that Young's modulus had higher sensitivity to changes in porosity and greater potential for clinical application. The results of the ex vivo experiments show that the bone thickness obtained by the inversion algorithm has a small error (mean error of 5.07%), and the theoretical dispersion curves corresponding to the inversion parameters match well with the measured data, verifying the feasibility of the inversion algorithm on real cortical bone. Since Young's modulus, Poisson's ratio, and cortical bone thickness provide a more comprehensive reflection of bone changes, they may be helpful in the prevention and treatment of osteoporosis.