Abstract: The fluid-structure interaction model and the acoustic-structure interaction model are two commonly-used theoretical models to analyze free vibration characteristics of submerged cylindrical shells. It has already been confirmed that the results are consistent when dealing with low-frequency free vibration problems, but no study was conducted to explain the cause behind. In this paper, free vibration characteristics of a submerged cylindrical shell are investigated based on both the fluid-structure interaction model and the acoustic-structure interaction model. According to Flügge theory, free vibration equations are established as well as related formulas. In order to apply the Galerkin method to solve the characteristic equations, the accurate data of natural frequencies of the system is first obtained, and the calculation efficiency is improved. Consistency analysis of the two theoretical models is also carried out based on the characters of the Bessel function, which indicates that the nature and the calculation samples of the two models are indeed consistent when dealing low-frequency free vibration problems, though the two methods which are based on different theories.