[Objectives] This paper aims to study the coupling relationship between the floating raft and the hull of the grid box, and propose a design method to enhance the vibration isolation effect of the floating raft-hull coupling structure. [Methods] The modal analysis of the grid box floating raft-hull coupling system structure and the independent floating raft and hull structure is carried out, and the floating raft structure in the coupled structure and the independent floating raft structure, the hull structure in the coupled structure and the independent hull structure are compared The first two modes of mode shape. The full frequency isolation effect of the coupling structure is analyzed, and the vibration isolation effects of the floating raft vibration isolation system and the independent floating raft vibration isolation system in the coupling structure are compared. [Results] Compared with the independent floating raft, the floating raft in the coupled system structure has little difference in natural frequency and mode shape, and the vibration isolation effect is also the same, indicating that the mutual influence between the floating raft and the hull is small, that is, the weak coupling relationship. The increase in the thickness of the floating raft panel and the weakening of the stiffness of the lower vibration isolator will improve the vibration isolation capability of the floating raft-hull coupling system. [Conclusions] The research results of this paper are helpful to improve the acoustic design of the floating raft-hull coupling structure system of similar grid box.