Abstract <p>The bolted joint dual-rotor system, connecting the high- and low-pressure rotors through an inter-shaft bearing, is extensively used in large-scale gas turbines due to its ease of assembly and high efficiency. Cracking failure in the inter-shaft bearing is a common form of malfunction that significantly impacts the engine’s safety and stable performance. This paper models a bolted joint dual-rotor system, taking into account the inner raceway defect of the inter-shaft bearing and the bolted joint’s time-varying bending stiffness. The aim is to provide a better understanding of the vibration and bending stiffness features of the bolted joint dual-rotor system. Through the numerical integration, the vibration waveforms, spectra, bending stiffness, and inter-shaft bearing forces with and without inner raceway defect are obtained and simulated. It is found that the presence of an inner raceway defect in the inter-shaft bearing results in new resonant peaks and causing additional frequency components. Moreover, the defect-induced impulse vibrations can induce a softened state in the bolted joint, generating continuous frequencies in the vibration spectra, especially at higher speeds. A test rig for the bolted joint dual-rotor setup, featuring an inter-shaft bearing with an inner raceway defect, is established to acquire vibration signals from the rotor. The experimental results provide the verification for the numerical simulation results. The analysis may prove reference for the simulation and bearing fault diagnosis of a bolted joint dual-rotor system.</p>