Abstract: In this paper, the sound propagation problem in a two-layer medium is studied and a finite element model for un-derwater sound field calculation is proposed. The finite element equation is derived by the traditional Galerkin method, and the four-node quadrilateral element is used to discretize the computation domain. Then the traditional radiation boundary condition, the DtN (Dirichlet to Neumann) non-local operator and perfectly matched layer are adopted to process the outgoing sound field and obtain the finite element solutions, and the differences between them are compared. In order to verify the finite element model, a benchmark solution is needed. Analytical solutions of sound propagation exist in a homogeneous medium. However, in a two-layer medium, there is no analytical solu-tion. Therefore, for the sound field calculation in a two-layer medium, the wavenumber integration method is used to provide benchmark solutions. The numerical simulations of sound field in a two-layer medium with limited and unlimited depths are conducted respectively. The results show that the finite element model is in good agreement with the benchmark solution. In addition, it is found that the normal mode model KRAKEN may be difficult to calculate the eigenvalue of the normal mode accurately when the eigenvalue of a normal mode is very close to the secant, so the error of sound field calculation result is significant; but the finite element method does not need to calculate the eigenvalues. Thus, the finite element model proposed in this paper can solve the sound field calculation problem where the KRAKEN model is hard to solve accurately, which means that the practicability of finite element method is better than that of the normal mode method.