The long-term meteorological data of Chongqing in the period of 1973-2010 are used to analyze the spatial and temporal distribution of fog days and the influence of climate change on them.The results show that,temporally,autumn and winter have more fog days than spring and summer in Chongqing and,spatially, the mid-west of the municipality has more fog days than its southeast and northeast regions.As for its west region,the north part has more fog days than the south part.Based on the temporal evolution of fog days,the 34 meteorological stations of Chongqing are divided into 3 districts,i.e.District I,including 20 stations in the main urban area and middle,west and southwest regions,with the Beibei Station as their representative, District II,including 9 stations in the areas west to its southeast and northeast regions,with the Wanzhou Station as their representative,and District III,including 5 stations in the areas east to its northeast region,with the Yunyang Station as their representative.The average data of Chongqing can perfectly represent the changing trend of DistrictⅠand can represent DistrictⅡ nicely,but cannot represent DistrictⅢ.In the recent 38 years,the average fog days in the whole region,DistrictⅠand DistrictⅡshow a significant linear decrease trend,at a rate of-2.9 d/10 a,-3.2 d/10 a,and -3.9 d/10 a,respectively.The average annual fog days show an increasing trend before the 1990's and decrease after that.The phase changes of fog days during the four seasons and the annual fog days are consistent.The fog days in the four seasons are generally in a linear decreasing trend,the fog days in summer are reducing significantly compared to the other seasons.Changes in temperature and humidity in Chongqing are closely related to variations in fog days.Fog days are in a negative correlation with temperature.Whenever the average temperature rises by 1℃,the fog days in most parts of Chongqing are reduced by 1-30 d.The reducing range in the middle and the northern regions is more significant than that in the northeastern region;the average fog days may be reduced by about 8 d in the whole region.Fog days are in a positive correlation with humidity.Whenever the average relative humidity increases by 1%,fog days in most parts of Chongqing may increase by 1-6 d,the range of increase is greater in the northwestern and northern regions than in the northeastern and southeastern regions,and the fog days in the whole Chongqing area will be increased by 3 d on the average.