Abstract: In order to master the occurrence rule of fog and difference between fog and haze in Yangquan, the observed fog data and haze data, the conventional meteorological data were studied with statistical analysis method to analyze the climatic features of fog. The difference of climatic features between fog and haze was also revealed. The results indicated that: owing to effects of temperature rise, decline of annual relative humidity and precipitation, the number of fog days of the whole year and every season increased firstly and then decreased from 1955 to 2012. Fog days increased significantly in the 1970s and decreased conspicuously in the first decade of the 21st century. The seasonal and monthly variations of fog occurrence were obviously. By the comparison between fog and haze, during 1975 to 2012, fog days decreased notably, while haze days increased significantly. Fog days and haze days showed obvious seasonal and monthly variation characteristics, in every season, fog days were less than haze days, and except August and September, fog days were less than haze days in other months. The study of difference between fog and haze climatic characteristics could provide a scientific basis for their observation and forecast.