The analysis of underwater structure vibration and noise control has been paid more attention now. The problem about propeller exciting force transfers from shafting, the bearing supporting to structure, causing structure radiated noise is less studied. It is necessary to study the characteristic of coupled system for solving such problem. In this paper, the characteristic of shafting and underwater structure coupled system vibration power flow is analyzed by numerical method and experimental method. The finite element method was adopted to build the analysis model. The force transfer ratio at each bearing supporting are calculated. The transfer function from propeller force to structure response are studied. The vibration characteristics of coupled system are got by numerical method and experimental method. The results show that the coupling vibration effect of shafting and shell are significantly especially at low frequency. The whole coupled system can be excited by propeller force. Some methods should be proposed to reduce this kind of vibration.