For wing-in-ground vehicles, ground effect increases lift force, which is mostly affected by wingspan. Four rectangular NACA4412 wings with varied aspect ratios were chosen to explore the influence of wingspan on aerodynamic properties in ground effect, and their aerodynamics were studied using CFD modeling. To simulate the flow around the wing in ground effect, SST k– \(\omega\) model was utilized. The overset technique was used to achieve varied pitch angle and altitude states where the wing operates. Results demonstrate that as wingspan increases, the variation rate of lift coefficient with respect to pitch angle or altitude increases, especially when pitch angle is less than 2 \(^\circ\) and relative altitude is less than 0.3. While a smaller wingspan causes a greater varying rate of downwash angle with pitch angle or altitude, when a wing has a smaller span and its relative altitude is less than 0.3, the development of the wingtip vortex becomes a stronger restriction for the block of ground, significantly reducing the downwash angle. The distance between the aerodynamic centers of altitude and pitch angle decreases as the wingspan expands, and the maximum magnitudes of change in chord length reach 0.045 and 0.2749 of chord length when the aspect ratio shifts from 1 to 4. The aspect ratio has no discernible effect on the boundary of static stability. When the aspect ratio increases from 1 to 4, the center of gravity must be moved upstream to ensure motion stability, and the maximum distance is 0.098 of the chord length.
