considering the Combination of several typical rotor unbalance conditions andpossible arrangments of magnet damper. rotor unbalance vibration of a large BBC turbine-genera-tor set has been analyzed by finite element method. Lincar simplification of dynamical characteris-tics of journal bearing and magnet damper was taken into account in the analysis.Numerical resultsshow that the optimum vibration control effect could be achieved when the damper located at middlepressure stage.