Abstract: Based on the ground meteorological observations, satellite remote sensing data and ERA-Interim reanalysis data, the dense fog weather which caused a traffic accident in Anhui Province during the night on 14 November in 2017 to the next morning were analyzed.The results showed that the dense fog was widespread and had the significant regional differences.The visibility in some areas of the central Anhui midwest and the West along Huaihe River was less than 200 m, the minimum visibility in the section where the accident happened was even less than 100 m; the high localized variations of visibility enhanced the difficulty of driving in highway.The dense fog event occurred in the background of west-northwest flow controlled on 500 hPa height field in Anhui without strong cold air, and homogenous pressure field with weak east water vapour transportation was existed on the surface.This was a typical radiation fog with the characteristics of less cloudiness, obvious radiation cooling and stable atmospheric stratification.Adequate water vapour supply and strong radiation cooling made air relative humidity reaching saturation at night.The stable atmospheric stratification and the near saturated atmosphere led to the dense fog event.