In this paper, the nonlinear dynamic of a composite rotor-bearing system with multi-degree-of-freedom are analyzed. The composite rotor is supported by sliding bearing, with a base loosening fault at one end. The orthotropic anisotropy of composite materials, the nonlinear oil film force and pedestal looseness are fully considered. Then, the motion equations of the composite rotor-bearing system are established by the lumped mass model. Various nonlinear phenomena compressing periodic, quasi-periodic and chaotic motions of the composite rotor system are analyzed. The results show that the rotor system is unstable in the form of oil film instability at low speeds and loosening instability at high speeds. The laminate parameters has an important impact on the stability of the rotor system. The ratio of the small orientation angle layer or the ± 45° layer shall be maximized so as to improve the oil film instability speed of the composite rotor system. While the loosening instability speed mainly depends on the stiffness of the composite rotor.