Abstract: Rub-impact between the oil pipe and floating tile of a tubular turbine under excitation by multi-fault source coupling could cause the aggravation of its vibrations and oil leakage that reduce its operating safety considerably. Considering the time-varying nonlinear oil film forces, this study develops a coupling dynamic model for a tubular turbine system with misalignment and rub-impact, and examines their effects on the dynamic behaviors of the system under interaction with the oil impurities and radial stiffness of the oil receiver. Results show that the system undergoes diverse nonlinear motions such as periodic motions and quasi-periods corresponding to different magnitudes of misalignment, featured with a vibration spectrum dominated by various low frequencies and large amplitudes. And working oil impurity induces the occurrence of rub-impact; the harmonic components become more complicated under the coupling effect and mutual excitation of misalignment, rub-impact and oil film forces. Moreover, reduction in the radial stiffness of oil supply may lead to an unstable chaotic state of the system. The results would lay a theoretical basis for safe operation and multi-fault diagnosis of hydropower units.