Fog with the size of 5～50 μm is simulated with an ultrasonic atomizer. A He Ne laser source at 0.63 μm is used to investigate the degree of the depolarization of the backscattered wave from those tiny water drop. It is shown that the degree of depolarization characters of those man made fog have a gravity dependence in a specified direction, and demonstrated an opto electronic effect in the depolarization of the fog.