Abstract: Three-dimensional unstructured Cartesian grid was used to solve the Naiver-Stokes equation and numerically investigate the wing-in-ground effect of a wing model. This wing model of a NACA4415 profile with an aspect ratio of 2.33. It contains a 20% chord, full-span, adjustable flap and removable centre and end plates. The ground effects were investigated in terms of angles of attack, relative height between the wing and ground, the existence and size of centre and end plates. Numerical results show that the ground effects are limited with relative height between the wing and ground higher than one mean chord. The usage of end plates can effectively improve the lift-to-drag ratio of wing-in-ground.