Using regular ground observations, sounding data, Shanghai Pudong Airport routine surface meteorological observations, statistic analysis of the climatic characteristics and the weather situations of advection fog at Pudong Airport has been carried out. The study found that advection fogs at Pudong Airport occur more and last longer year by year, mainly concentrate in winter and spring, appear at anytime in a day, mostly are southeast surface wind, and mainly occur in five specific weather situations which are "behind the high-pressure system entering the sea", "at the northwest side of the subtropical", "before the cyclone", "outside the typhoon", "before the high-pressure system". Using the visibility data with time resolution of one minute from Pudong airport Automatic Weather Observation System(AWOS) 2007-2009, the heavy advection fogs with visibility below 200 meters were analyzed. The results found that a number of proccesses are necessary for the outbreak of a heavy fog event. Before the main body of heavy advection fog's coming, there is a large-amplitude oscillation which shows obvious "trunk-like" fluctuating forepart at the visibility map. This feature provides a basis for monitoring and warning of advection fog.