In accordance with the timely weather report and routine meteorological resources of the meteorological observatory of Liaoning Province from 1979 to 2009,durative fog occurred in Liaoning and their characteristics were counted and analyzed in this paper.The report showed that the continuous hazy days occurred three times in 30 years and they had large chances to take place in winter.After the heavy precipitation in the North China and Northeast China,temperature in every place turned up again.If under such circumstances,expansion and temperature inversion happened in the 925 hPa and the wind speed was slower than 4 to 8 m/s in the 1 000 hPa,continuous hazy days happened.
