Based on the meteorological observation data of visibilty, relative humidity, and precipitation from expressway automatic weather observation stations in Anhui from 2011 to 2015, the annual distrbution and diurnal variation characteristics in each seasons of low visibility in Anhui are analyzed. Results show that the low visibility events occur in October and November mostly except those happened between May and September in the mountain areas such as the Dabie Mountains and the southern mountainous areas of Anhui. The low visibilty events have remarkable diurnal variation with the frequency at night being much higher. The low visibilty events begin to increase at 19:00, reach a highest point before sunrise, then decrease rapidly. The low visibility events in summer in 〖JP2〗the afternoon are related to heavy rainfall. Seasonal differences exist in time and frequency of the low visibility: occurring mostly around sunrise in spring and autumn while at night before sunrise in winter; occurring before the sunrise in the nothern Anhuit, and no significant differences in the frequence during a day in the southern Anhui in summer.〖JP〗