Abstract: A finite element method based on the added mass method is presented to simulate the water-exit process of an underwater vehicle. Starting from the modal experimental data of vibration in the water-exit process, transient distributions of added mass on the structure are derived from the frequencies of transverse vibrations. The dynamic behavior of the underwater vehicle during the water-exit process is studied. Investigations are carried out upon the transient response of the bending moment and transverse force on some key cross-sections. In contrast to the situation where there is no added mass, the frequencies are lower with the added mass. However, the magnitude of vibrations is not the case. Frequencies grow as the water-exit length grows in the computations. This result qualitatively validates the time-varying transverse added mass method and lays the foundation of further research on the added-mass-based FEM.