Abstract:A sustained foghaze event that occurred in early December 2013 in Yancheng was analyzed based on surface meteorological parameters, NCEP reanalysis data (1°×1°), and air pollutants concentration. The study focus lies in circulation background, surface meteorological elements and atmospheric stratification feature, as well as thermodymamic condition and pollution. The results show that there were weak cold air forces in middlehigh level in early December with zonal circulation at 500 hPa. The breezed surface layer was the favorable circulation background for the formation of foghaze. The maintenance of stable stratification characteristics, high inversion intensity and continuous lower mixed layer were responsible for the sustained foghaze briefly. In addition, the weak sinking motion, positive divergence and negative vorticity were the dynamic factors for the sustain development of foghaze. The longdistance transport of pollutants played a certain role in the concentration increase of pollutant particulates according to the backward trajectory types and the monitored fire spots. Finally, the nonlinear regression formula of visibility, humility and PM2.5 concentration was established, which is better for visibility forecasting and provides a favorable basis for the operation of foghaze forecasting.