Abstract: The author described the distribute regulation of spatial-temporal variation of fog days by analyzing observational data including annual variation, seasonal variation, monthly variation and geographical distribution of 17 meteorological stations. This information could be basically used to forecast the occurrence of fog and provide scientific basis for preventing harm from fog and improving living environment. The results showed that: mean fog days of the 17 observation stations increased slowly during the 30 years, whereas the highest value appeared at 2006 which was 19.6 days; only 4.4 days was observed at 2010 which was the lowest value. These results indicated that: the annual variation was tremendous. The difference of regional distribution of fog days was apparent, and fog days of plain were far more than mountain area. Variation tendencies were not identical between each other of the 17 observation stations. During the 10 observation stations fluctuant increasing fog days were observed, Anze had the highest increment of climate tendency quotiety in 30 years. Contrarily, Linfen declined fastest during the remaining 7 observation stations that climate tendency quotiety decreased in 30 years. Fog mainly aroused in autumn, especially in October which account for 18.07% of the fog days all the year round. However, only a very small fraction of fog days appeared in spring, for instance only 3.20% of the fog days were in May. Seasonal variation was very evident of fog days in Linfen, and fog days took place more frequent in central region in spring, autumn, winter, but concentrated in central- northerly in summer.