Vibration is a major issue in rotor systems. Due to the presence of material property dispersions, manufacture or assembling errors and time-varying working status, rotor systems are always subject to uncertainties. The uncertainties should be taken into consideration to understand the dynamic characteristics of rotors more thoroughly. In this study, interval analysis is carried out to investigate the non-probabilistic characteristics of a double-disk rotor with uncertain parameters. The uncertainties are modeled as uncertain-but-bounded variables due to insufficient essential information to define their precise probabilistic distributions. The deterministic analysis model is derived by the finite element method (FEM). The accuracy and effectiveness of the proposed method in solving uncertain rotor problems are validated by comparative study with the Monte Carlo simulation (MCS). Several cases where different physical parameters are regarded as uncertain are investigated and the dynamic response bounds are obtained. Simulations suggest that uncertainties have significant influence on the dynamic characteristics of the rotor system. Multi-source uncertainties propagation can cause heavy vibrations in mechanical systems.