The event of an advection fog occurred in Jiangsu Province during 18-19 March 2013. It firstly formed in the north bank of Yangtze River and then spread to northern Jiangsu Province. In this study, the formation mechanism and characteristics of this fog event are analyzed, and the transmission mechanism of the fog is particularly emphasized. The results indicate that this advection fog event was formed by the influence of warm and humid advection after being controlled by cold air. The cold front transit was the basic condition for the formation of advection fog. The north lift of the denatured cold high pressure from East China Sea was helpful for the formation of this advection fog event. The fog area moved northward as the result of the promoting role of southeast wind from the ground and watervapor transfer toward southeast at low altitude. The waters of Yangtze River, Hongze Lake and Gaoyou Lake played significant roles in enhancing the development of the advection fog. The heavy fog developed gradually with insignificant explosive increase and coexistence of cloud and fog as the main characteristics. These findings have practical values to the forecasting of advection fog.