Taking the structural characteristics and the complexity operating environment of the whole aeroengine system as the research background, the Lagrange approach was employed to establish the flexuraltorsional dynamic model for a doubledisk rotor subjected to the influence of imbalance exciting force and axial movement caused by the thermal expansion. Due to the axial movement of the shaft caused by the nonuniform distribution of temperature and thermal expansion properties, the analytical expressions of the surface rubbing force and moment were derived respectively. Finally the fourthorder RungeKutta method was adopted to solve the dynamic model. Numerical analysis on the dynamical response of the system shows that the temperature stress accumulated by thermal expansion, axial movement of the shaft, and surface rubbing moment, are all the key factors, which would change the inherent physical properties and cause flexuraltorsional vibration of the doubledisk rotor.