Wing-in-ground effect of NACA0012 at angle of attack of 18? was tested in a model wind tunnel. The velocity fluctuations in wake near the trailing edge were captured by 3D CTA. Unsteady flow of wing-in-ground effect in different flight height was analyzed based on the test results.The aim is to provide a reliable basis for the aerodynamic characteristics and control of unsteady flow of wing-in-ground effect at a high attack angle. It is shown that vortices near trailing edge of wing in ground effect at high angle of attack are shifted backwards in ground effect; with decrease of flight height, both the frequency and the