Abstract: Taking the rotor system supported by the combined bump foil air bearing previously proposed by the authors as the research object, a study on its dynamic performance is conducted. A fluid-structure interaction model of the gas foil bearing is established by simultaneously solving the Reynolds equation and the deformation equation of the foil structure. The perturbation method is employed to solve the dynamic Reynolds equation and calculate the dynamic performance coefficients of the foil bearing. A parameter-lumped model of the bearing-rotor system is developed, and the Riccati transfer matrix method is used to investigate its dynamic characteristics. The accuracy of the model is verified by comparing the first six modal frequencies obtained from hammer impact tests with those from model calculations. On this basis, a numerical study is conducted using specific calculation examples to investigate the influence of bearing structural parameters—such as bearing radial clearance, flat foil thickness, bump foil thickness, and bump arch half-length—on rotor dynamics performance, including critical speed and unbalanced response. Within a certain range: increasing the radial clearance and reducing the flat foil thickness can enhance the system stability, while selecting appropriate bump foil thickness and bump arch half-length can minimize the amplitude of the unbalanced response and further improve the system stability. This provides a theoretical reference for the design of combined bump foil air bearings and rotors.