Abstract: Unmanned aerial vehicle (UAV) trans-medium navigation is an important research field in recent years. In this paper, through numerical simulations, the flow field evolution and motion attitude of a flying wing UAV in the process of launching into water under different working conditions were compared and analyzed. At the same time, the numerical simulation of its water impact response was carried out to obtain the response of the UAV under water impact load for different launching conditions. The results show that the posture change of the UAV during water entry process is affected by both surface conditions and launch conditions. In hydrostatic condition, when the UAV is launched at 25° water entry angle and with speed of 4 m/s, the optimal attitude recovery time and response value of water entry impact load can be achieved.