The fog information of 59 Jiangsu groundbased observation stations from 1961 to 2007 is studied. The fog concentration degree (FCD) and fog concentration period (FCP) of annual fog days in Jiangsu province are selected to analyze the spatial and temporal distribution patterns and variations. Results show that the value is lower in coastal areas than in inland and there are higher values in the north and the south than in the middle of Jiangsu province. FCP shows the significant fluctuation during 47 a. With the Empirical Orthogonal Function (EOF) method, the first eigenvectors of the anomalies of fog days, the FCD and FCP are in phase respectively. The corresponding time coefficients of fog days are higher in 1980s than in other period, and the corresponding time coefficients of both the FCD and FCP are decreasing before 1980 and then increasing subsequently. It is shown that the climatic tendency of fog days at all stations except four in the north of Jiangsu is increasing.