The dynamic behaviors of a flexible multi rotor system supported on journal bearing with a misaligned coupling were investigated. Firstly, the dynamic model of a rotor system under the action of the nonlinear oil film forces was developed after taking into account the movement relationships and displacement constraint, which describes the misalignment relation between two rotors, and the theoretical analysis reveals that the system with eleven DOF is of strong nonlinear properties and time varying parameter. Then, the nonlinear dynamic characteristics, such as steady state response, rotor orbit, Poincaré section and the largest Lyapunov exponent, were studied. The results show that, at low speed, the orbit synchronously oscillates within a small zone; as the speed increases, the dynamic characteristics become complicated, and the period doubling, quasi period and chaotic oscillations occur. Finally, the effects of the bolt stiffness on dynamic behaviors were also discussed.