The new SEA method developed in this dissertation is the integration of virtues from the mobility analysis, classical SEA and classical theory of power flow, which fits for vibration and noise analysis of complicated coupled systems. This research provides a theoretical base for study on vibration transfer between structures and noise radiation of complicated mechanical systems, and it also offers guidance for isolation and noise control of engineering structures. Contributions of this dissertation are as follows： First, in view of the disunion of SEA parameters in classical SEA, a union definition of SEA parameters is brought forward. Secondly, some elements that influence energy transfer between mechanical structures are separated and corresponding parameters are introduced to investigate those influences separately. (1)Linking style coefficient is introduced to denote the rule of vibration energy transfer when structures are linked at one point, some points or a line. (2) Non-conservative coupling coefficient is introduced to describe the influence of isolation or damping when structures are isolated or damped. (3) Indirect coupling coefficient is introduced to research the property of vibration energy transfer when two structures are indirectly linked by other structure. Thirdly, on the basis of above, gradation analysis is put forward to simplify the vibration analysis of complicated coupled system. Then, by using theoretical achievements above, the property of vibration and noise radiation of underwater vehicle is analyzed by the developed SEA for the first time. Levels of vibration and sound power induced by two different underwater vehicles are predicted. The analysis results agree well with experiment results. Finally, based on the analysis, the direction of noise control of underwater vehicle is pointed out.