The coupled bearing (including a tilting-pad journal and a thrust bearing) is mainly used in a nuclear power circulating pump to simultaneously support the high axial loads and radial loads of a vertical rotary system with minimum power loss, low vibration, and high load capacity. Its lubrication and vibration characteristics have significant effects on the operation reliability of the nuclear power circulating pump. In this paper, an original mixed-lubrication dynamic model for the coupled bearing-rotor system is proposed to study the dynamic characteristics of the system considering the effects of the pivot clearance, asperity contact, and elastic deformation. The innovation of the proposed model is that it integrates the horizontal-rocking vibrations of the rotor and pads with the mixed lubrication of the coupled bearing and the wear of journal pads and thrust pads. The effects of different external loads and pad wear levels on the dynamic characteristics of the coupled bearing-rotor system are revealed. Additionally, a series of experiments are performed to measure the vibration responses of the system, which are directly compared to the simulated responses of the proposed model for validation purposes. It is expected that the proposed mixed-lubrication dynamic model can provide practical engineering guidance for the condition monitoring and fault identification of coupled bearing-rotor systems.