For the numerical analysis of aircraft dynamic behavior in ditching, how to define the coupling effect between fluid and structure is the key problem, which determines the success or failure of the numerical analysis to some extent. A coupling method based on structural-arbitrary Lagrangian-Euler algorithm (S-ALE) was used to characterize the interaction between the aircraft and the water during the ditching. S-ALE fluid-structure interaction method was adopted to analyze the dynamical behavior of aircraft in ditching to extract the history of aircraft pitch attitude and overload, and the results were compared with those obtained by the traditional ALE penalty-based coupling method and experiments. It is shown that the S-ALE fluid-structure interaction method can prevent the fluid leakage and effectively predict the phenomenon of aircraft secondary rise, and the pitch attitude angle and overload curve predicted by the S-ALE fluid-structure interaction method are basically consistent with the experimental data.