With the daily fog data of 16 weather stations in Southeast Guizhou from 1961 to 2007, a detailed analysis is made of the daily, seasonal, annual, and interdecade variation characteristics and longterm trends of fog distribution over Southeast Guizhou. It is concluded that the maximum number of foggy days averagely occurred in the 1960s, and minimum in the 1980s, with an increasing trend after 2000; the greatest number of foggy days are found in autumn and the least in spring, the greatest in November and the least in February; there is a quasi40 year period and a quasi5 year period in the variation of the number of heavy fog days; heavy fog weather occurred most frequently around the central part of Southeast Guizhou and relatively less in the southeast and northwest parts of Southeast Guizhou.