Abstract: The fluid-filled multi-shell structure design is mostly used in submarines. The multi-shell structure consists of light shell and multi pressure shells. When it is exposed to attack by underwater weapons, the mechanism of transmission gets so complex that it has been a troublesome problem for a long time. In this paper, a numerical method was developed to solve the problem. The second-order doubly asymptotic approximations (DAA2) was used to analyze the external fluid-structure interaction (FSI) effect for the outer fluid field with the outer plates and cavitation acoustic finite element (CAFE) was used to model the internal FSI effect. Results obtained using this method showed good agreement with results of 3D fluid-filled spherical shell shock problem. Last, the method was validated by a fluid-filled multi-shell structure test. The velocity, acceleration and shock environment were compared with the test data. The research results show that the numerical method is accurate and have verified the effectiveness of the method.