As the air cushion and the wind both greatly affect the falling process of marine structures from the sky into the water，this paper proposes an air-solid coupled mathematical model to describe the falling slamming process of 3D complex structures． In the investigation，the falling mechanism of structures is analyzed，the air damping and the 6DOF (Degree of Freedom) motion characteristics are fully taken into consideration，and the three-dimension transient N-S equation，the turbulence dynamic equation，the energy equation and the rigid 6DOF kinematic equa-tion are comprehensively adopted． The proposed model is then applied to numerically simulate the falling slamming process of a structure from the air into the water，and the results are compared with those obtained by the physical model，finding that the proposed model is effective in simulating the falling slamming process． Moreover，from the simulated results obtained at different falling heights or in different wind blow environments，it is found that (1) the existence of air cushion changes not only the structure slamming speed but also the pressure distribution; (2) the slamming may result in a temperature rise of the air cushion; and (3) the wind blow changes the falling pose of structures and makes the structures fall from the air with a“zigzag”pose and then slam into the water．