From the analysis on wavefront aberration caused by high-speed airflow, it was found that aero-optics inhomogeneity is consisted of large-scale ordered and small-scale random inhomogeneity. With wavefront sensor, the large-scale aberration can be reconstructed. For the small-scale aberration, the coherent index is a better standard for measurement. However, the Lateral Shear Interferometer (LSI) can realize the two kinds of measurements. Therefore, the inhomogeneity of Free Vortex Dynamic Window (FVDW) was investigated by LSI, the one dimension wavefront aberration in output window was reconstructed and the random inhomogeneous scale distribution was given. Also, the main cause of inhomogeneity was discussed.