To study the nonlinear vibration characteristics of dual rotor systems considering the elastohydrodynamic lubrication (EHL) of intershaft bearings, an intershaft bearing contact model and an intershaft bearing-dual rotor system model for aero-engine were established based on the EHL theory and the rotor dynamics theory. The dynamic characteristics of the system were obtained by numerical simulation. The amplitude-frequency response of the dual rotor system was analyzed under the conditions with or without EHL. The influences of Hertz contact stiffness, radial clearance, and viscosity of lubricating oil of intershaft bearing on the system characteristics were compared. Results show that EHL had little effect on the vibration amplitude and the position of the resonant peak of the high pressure rotor and low pressure rotor at the first order resonant peak, while it had great effect on the resonant peak in the high speed range, which made the resonant peak move to the right and decreased its amplitude. With varying Hertz contact stiffness and radial clearance of intershaft bearing, the variation of amplitude at the first order resonant peak was less than 5% when considering EHL, and that at the second order resonant peak was between 4% and 9%. The position of the first order resonant peak was not offset, while that of the second order resonant peak moved about 2%–8% to the high-frequency direction. The influence on the vibration amplitude of the low pressure rotor and high pressure rotor was less than 1% when the viscosity of lubricating oil was changed. Finally, simulation results were validated by gas-driven dual rotor experimental facility.