Abstract: To improve the communication capacity of air-to-ground (ATG) downlinks, the three-dimensional geometrically based single bounce concentric elliptic ring scattering (GBSBCERS) channel model of ATG multiple input multiple output (MIMO) was set up. Combing with the linear array layout and circular array layout of airborne MIMO, the analytic formula of airborne MIMO channel correlation matrix and ergodic capacity was deduced based on array structures. Then the influence of array structures on the ergodic capacity was analyzed to improve the ATG transmission rate by means of antennas layout. The simulation results shown that the MIMO channel capacity will increase along with the increase of antenna distance in the influence of ATG remote communication, and the circular antenna layout which has more channel capacity than linear antenna layout can adapt to the UAV attitude change.