Abstract: Objectives In this paper, the floating raft and hull is modeled as a whole system. The study of vibration and sound radiation characteristics of the floating raft and hull coupled system is conducted to enhancing the acoustic performance of the coupling system. Methods The floating raft and hull coupling dynamic system is simplified as a reinforced cylindrical shell, double-layer plates, springs and surrounding acoustic medium. The vibration energy equations of the structural domain are derived base on the generalized variational method and the discrete boundary element equations for the acoustic field domain are established based on the Kirchhoff-Helmholtz integral method. By expanding the vibration displacement and acoustic pressure into a Fourier series and polynomials in the vibration energy equation and the Kirchhoff-Helmholtz integral equation, then the governing equations of the floating raft and hull coupling system are developed. After that, the verification of the dynamics model is carried out base on FEM simulation method. Finally, based on the dynamic model of the coupling system established, the influence law of the design parameters of the floating raft and hull structure on the dynamic characteristics of the coupled system are put forward. Results The proposed results of the dynamics model for the floating raft and hull coupling system are consistent with those of the finite element method (FEM). Thus the accuracy of the dynamics model based on generalized variational method proposed in this paper is validated. Moreover the method proposed has the advantages of high analytical efficiency and clear mechanism. In addition, based on the dynamic model, the research has revealed the influence law and optimization design methods of various design parameters including the stiffness of the isolator, the elastic modal of the raft, the mass ratio of the raft to the equipment, and the structural parameters of the hull on the acoustic performance of the floating raft and hull coupling system. Conclusions The proposed semi-analytical method is accurate and efficient. The research can provide significant support for dynamic analysis and optimization design of floating raft and hull coupling system which is of great significant in practical engineering.