Abstract: This paper analyses the drift data of the digisonde (DGS-256) at Millstone Hill (288.5°E, 42.6°N ) The result shows that the propagation direction of ionospheric gravity wave disturbances rotates clockwise throughout the day, the maximum of the disturbances occurrence is at the angles between 180°and 225° reative to the caiculated direction of background wind. Evidentiy, the result implies that disturbanas are wind filtered. Further analysis shows that the smaller the disturbance's scale, the more obvious it propagathe on the opposite direction of wind.