Abstract: The climatic characteristics of fog,including the spatial and temporal distributions,season and monthly frequency distributions,and the interannual variation trend of fog days,were analyzed with 50 years’observation data(1961 to 2010),from 84 meteorological stations in Guizhou.It showed that: there are four main fog zones in Guizhou: the western fog zone,mainly distributing in east Wumeng Mountain;the central fog zone,lying on the region of Kaiyang and Xifeng County;the east fog zone,mainly rounding the Miaoling mountain and Wanshan DC in Tongren District;the southwest fog zone,outward extending from Qinglong County.Heavy fogs mostly occur in the winter,Secondly in spring,then autumn,the least frequency in summer.The most fog days appear in December,January and October,and the least in May,Jun and July.Heavy fogs arise in the morning,seldom in noon and evening.Interannual changes of heavy fogs show significant trend in the past 50 years(at 0.05 reliability test),but a slightly decreasing in this century.