Based on the 6hour data of weather phenomena, visibility and common meteorological elements from 1981 to 2013 from 125 observation stations over Yunnan, considering the terrain heights, by means of the high resolution meteorological element interpolation method and the objective identification model of meteorological elements for foggy weather unsuitable for flights (the heavy fog with visibility less than 800 m), the influence of visual obstruction weather on airworthiness conditions and its climatic characteristics in Yunnan are analyzed. The results indicate that the primary visual obstruction weather in Yunnan was fog and mist, but the visual obstruction weather affecting airworthiness conditions was fog. Foggy weather unsuitable for flights has a close relationship with relative humidity (RH), wind speed (WS), and the difference of surface temperature and air temperature (〖WTBX〗T〖WTBZ〗s-〖WTBX〗T〖WTBZ〗a); moreover, the key point of occurrence and maintenance of foggy weather unsuitable for flights is the stable meteorological conditions of high humidity and weak wind, with the quantitative indicators: RH>98%, WS<3 m/s, (〖WTBX〗T〖WTBZ〗s-〖WTBX〗T〖WTBZ〗a)<3 ℃. The southern, southwestern and eastern Yunnan Province are the regions where foggy weather unsuitable for flights frequently occurres, especially JingdongSimaoXishuangbanna, XimengLancang, BaoshanTengchong, Luoping, etc. To compared with the data of observation stations, the spatial distribution of foggy weather unsuitable for flights judged by the high resolution data by the objective method has better correspondence with terrain, which can reasonably reflect the spatial distribution characteristics of complex terrain, while the middle, western and northeastern Yunnan are on the contrary.