Heavy fog occured for five successive days from Dec. 27 to 31,1996. Using a drop size meter and ADAS,soundings of microphysical structures of radiation fog and soundings of vertical distributions of some related meteorological elements,such as temperature,pressure,moisture,wind and so on were conducted. By analysing these data thoroughly,the microphysical structure characteristics and evolution processes of radiation fog in Huning region were discovered. Results suggest that there is a close connection between the microphysical structures of fog and the degree of air pollution,and a long lived inversion has an effect on the former. Furthermore,quasi periodic oscillations with periods of 20～30 minutes are observed in liquid water content,spectrum width,and peak diameter etc..