Using the minutely data including visibility, relative humidity, temperature and wind speed of 36 automatic weather stations along the Yangtze River in Jiangsu Province during 2010-2013, the characteristics of river fogs are analyzed. The results show that river fog mainly occurs in June, November and January, formed from 19:00 BT to the next 07:00 BT, during which the fog is the thickest in 02:00-04:00 BT and gets to end from 06:00 BT to 12:00 BT, so the fog duration is 3-9 h. When fog occurs, relative humidity is 85% or higher, temperature is 5-19℃ in spring, 18-26℃ in summer, 7-23℃ in autumn and 0-11℃ in winter. As for the wind speed, it is below 5 m·s-1 in spring, summer, autumn, and about 6 m·s-1 in winter. Specifically, the fog tends to occur with the wind direction of NNE-E and wind speed 1-2 m·s-1 in spring, the wind direction of NNE-ESE and wind speed 0.3-1 m·s-1 in summer, the wind direction of NNE-NE and E-ESE, wind speed 0.3-2 m·s-1 in autumn, and the wind direction of NNE-NE and WNW, wind speed 1-2 m·s-1 in winter. In addition, by analyzing the visibility changes of the first station in the fog, we found that there are obvious “trunklike” characteristics before river fogs develop. Such features could provide the basis for the operation of early warning and forecasting of river fogs.