Based on the meteorological observations at Nanjing Meterological Observatory and other five suburban meteorological stations(Jiangpu, Luhe, Lishui, Jiangning and Gaochun) during 1961-2006, the climatological characteristics of fogs in Nanjing and their relationships with various meteorological parameters are analyzed. Results show that, depending on the topography and the nature of underlying surface, the occurrences of fog events at these six locations are different. The fog processes are more likely to happen at Lishui, Luhe and Nanjing than at other three places(Jiangpu, Jiangning and Gaochun) with the highest frequency of fogs(34.9 days annually) at Lishui. Fog events at six stations show the same seasonal characteristics with the maximum frequency in winter and autumn, the next in spring and the minimum in summer. It is also found that the annual fog days at Lishui, Gaochun and Jiangpu are increasing and an opposite tendency occures at Nanjing, Jiangning and Luhe. Results reveal that the fog events are more likely to occur under the conditions of weak surface wind, high humidity and weak high system.