Abstract: In view of the current situation that numerical methods have been used to solve the acoustic-structure interaction of conical-cylindrical combined shells near a water surface,a semi-analytical method is proposed to analyze the above problem based on its physical mechanism.Firstly,the structural model of conical-cylindrical combined shell is established based on energy functional theory,Sanders' shell theory,virtual spring method,and force and moment equilibrium conditions.Then the Legendre spectral element method and two-dimensional Fourier transform are used to obtain the underwater acoustic field model with a free surface.Finally,nonlinear iterative method and the Gauss integration are used to calculate the vibration and underwater acoustic radiation.The convergence,correctness and reliability of the method in this paper are verified by comparing with the results of previous references and numerical methods.The results show that the structural parameters,submergence depths and excitation frequencies are closely related to the far-field sound radiation.The study in this paper can be extended to the problem of acoustic-structure interaction of underwater complex rotating combined shells containing internal structures at different structural and acoustic boundaries.