Abstract:With the rapid development of highway communication, the influences of th e dense fog on the transportation system are becoming more and more serious. The dense fog often leads to the traffic accident, and gives rise to tremendous los s to the lives and the property of people，thus it is very harmful. By using the meteorological data from 1957 to 2006, the characteristics of the temporal and spatial distributions on the dense fog in its inland and the c oastal area of Qinhuangdao City are analyzed, and by means of the historic synoptic c harts from 1981 to 2000, the synoptic patterns of the dense fog are also obtained. The major meteorological elements influencing the dense fog are selected fr om many factors, and thereby the equation of the MOS forecast about the dense fo g is set up. That will offer a strong support to the forecast of the dense fog, the issuance of early warning signal and its annulment. Therefrom, the purpose o f monitoring and forecasting the dense fog will be achieved.