Ship hull vibration is much complicated phenomenon because of the complexity of interaction between the vibration characteristic of ship hull, main engine, and shaft system (crank shaft through propeller) structure. To cope with this problem, we developed new method that is to analyze 1. Dynamic interaction between ship hull and main engine by means of substructure approach connecting each vibration characteristic of ship hull and main engine structure, 2. Vibratory response considering the influence of moving/rotating parts in main engine, and 3. Contribution of each exciting force to the vibratory response of the superstructure. By this means, we proved that the characteristics of the exciting force from the shaft is much influenced by the vibratory characteristic of the shaft, the axial force acting on the thrust block and the axial damper has much influence to the superstructure vibration. Also we showed that the reduction of axial force ispossible through the control of the vibratory characteristic of the shaft system.