In the process of maneuvering flight， the aeroengine will bear very harsh working conditions， leading to irregular tran? sient vibrations that can result in failure. In this paper， the effect of a semi-active magnetorheological damper （MR damper） on the dynamic characteristics of a rotor system under maneuvering flight is investigated. The finite element model of the rotor system with MR damper under maneuvering flight is established using the finite element method. The Newmark- β numerical method is used to solve the dynamic equations， and the dynamic characteristics of the rotor system during maneuvering flight are studied. On this basis， considering the effects of MR damper on the transient， the steady state responses of the rotor system under maneuvering flight are analyzed. The results show that transient impact is caused at the beginning and the end of maneuvering flight， which stim? ulates the first order modal response of the rotor system. The MR damper with suitable current can effectively suppress the ampli? tudes of transient and steady-state responses of the rotor system during maneuvering flight. In addition， due to the large eccentricity of the journal in maneuvering flight， the MR damper is prone to produce nonlinearity.