Using foggy days and mean temperature and relative humidity data of 602 stations from January to December in the period 1961–2003 in China, the relationship between variations of foggy days and temperature and its possible reason for the 43 years were analyzed by regression, correlation and contrastive analysis methods. The results show that the higher (lower) the mean temperature and the lower (higher) the relative humidity correspond to less (more) foggy days, the relationship is the best in the western, northern and eastern Sichuan, Yunnan-Guizhou Plateau, and southeast highland in China. This induces a decrease in relative humidity when the climate becomes warmer, and eventually brings about a decrease in foggy days in China.