Climatic characteristics of mountain fog and mist in Xuan'en,west Hubei province are analyzed based on the meteorological data collected from observational station in the period 1959-2009.It is shown that the average fog day is 29 annually and the annual fog days present a decreasing variation trend.The fog events occur in every month with the maximum frequency in winter,the next in autumn and the minimum in summer.It is also found that the annual mist days are generally increasing but there is an opposite tendency with annual fog days.The monthly average mist days in each month are between 9 and 15 with the maximum in December and the minimum in May.Furthermore,studies of the characteristics of meteorological elements point out that the annually average minimum air temperature is rising,the annual average relative humidity at 08:00 and the annual rainfall vary unobviously and the annual days of visibility at 14:00 greater than 20 km are decreasing.Results reveal that the unsymmetrical variation characteristics of fog and mist occurrence frequency probably have the correlation with the increasing aerosol in atmosphere.