Taking the dual rotor system in the aero-engine as the research object, the vibration behaviors of the dual rotor bearing system with fault-free, misalignment fault, rub impact fault and misalignment rub impact coupling fault are studied, respectively. Firstly, the three-dimensional model of the dual rotor bearing system is established, and then the first six modes and critical speeds of the dual rotor bearing system are obtained by the finite element method. Then, the dynamic equations of the dual rotor bearing system with fault-free, misalignment fault, rub-impact fault and misalignment rub-impact coupling fault are derived based on the Lagrange method. The Runge-Kutta method is used to solve the dynamic equation, and the nonlinear dynamic response of the system is obtained. The vibration behaviors of the dual rotor system with misalignment fault, rub-impact fault and misalignment rub impact coupling fault are analyzed and discussed through the time history, phase diagram, and frequency spectrum of the rotor. The vibration behaviors of the first six modes of the dual rotor system with fault-free, misalignment fault, rub-impact fault and misalignment rub-impact coupling fault are analyzed, respectively. The results can provide theoretical guidance for structural optimization design of the aero-engine rotor system and the prior decision information for misalignment and rub-impact coupling fault diagnosis.