The aim of this paper is to gain insight into dynamic characteristics of a dualrotor system in the absence and presence of a nonlinear energy sink. Firstly, the governing equations of motion of the dual-rotor system are derived by the Lagrange’s equation. Then the dynamic characteristics of the system in the different conditions of rotational speed ratio are investigated. On this basis, a nonlinear energy sink is introduced in the LP rotor, where the effects of rotational speed ratio on the optimization of control parameters are taken into account. At last, the vibration suppression of the dual-rotor system is carried out. Moreover, the parameters analysis of the system is accomplished as well.