In order to study Siemens- Schottel- Propulsion (SSP) vibration for the marine electrical propulsion system, the SSP vibration analysis has been carried out in this paper. SSP suffers from harmonic vibration and torsional vibration of propeller and wave flow random disturbances. Vibration mode superposition method is applied to SSP vibration model. The SSP dynamic model has also been established based on SimMechanics. The simulation results show that the proposed way is important to forecast and prevent SSP vibration and to provide for the SSP management.