To study the effect of different courses of ditching on wavy water, a sliding dynamic grid method based on rigid dynamic grid and sliding grid is developed. While ensuring that the free surface is in the grid encryption area, it is possible to simulate any attitude of the airplane under complicated sea conditions. By simulating three-dimensional rectangular flat plate oblique impact into water, the vertical movement history and the pressure distribution are compared with experimental data to verify the effectiveness of numerical method, and the grid parameter setting experience is also got. The simulation results of airplane ditching on calm water using sliding dynamic grid method are compared with experimental data to verify the effectiveness of sliding dynamic grid method. On the basis of application of wave making method, numerical simulation of three different ditching courses on wavy water, such as heading waves, following waves and parallel to waves are made. By comparing and analyzing the movement history and the force of different parts, it is concluded that the optimal course of ditching on wavy water is parallel to waves, the vertical impact peak is 12% larger than that on calm water, and the effects of roll and yaw motion is small. The most dangerous situation is heading waves, which will produce larger pitch angle, the vertical impact peak is 149% larger than that of calm water ditching, and will suffer many wave impacts.