In this paper, the dynamic equation of rigid-elastic coupling elastic aircraft is established based on Lagrange method. The landing characteristic of the Global Hawk UAV with large aspect ratio are simulated and analyzed under the parameters of modal mass, generalized installation displacement, frequency and structural damping coefficient. The results show that the elastic modal mass and the generalized displacement of the mounting point can affect the load, stroke, speed of the aircraft buffer and tire support reaction. The smaller the modal mass, the larger the generalized displacement of the mounting point and the smaller the load of the buffer. Generalized displacement of installation point, structural damping coefficient and elastic vibration frequency of body can affect the energy dissipation efficiency of landing impact. The larger the generalized displacement of installation point, the larger the structural damping coefficient, the smaller the elastic vibration frequency and the faster the impact dissipation rate of landing.