Abstract: Enshi is a foggy area in Hubei Province with complex terrain and large spatial difference in fog. However, the meteorological stations in this area are sparse, making it difficult to study the spatio-temporal distribution characteristics of fog. This paper uses the land surface data from CLDAS (China Meteorological Administration Land Data Assimilation System) and the Enshi station to analyze the spatiotemporal characteristics of fogging potential index in the Enshi area. The results are show below. (1) According to the hourly data of Enshi station in the past 30 years, a high relative humidity over 90% and a small difference (≤2.0 ℃) between actual temperature and dew point temperature (T-T_d) are favorable for fogging. (2) The diurnal variation of fogging potential index based on the CLDAS data and the observations in the Enshi area are consistent and correlated. Therefore, the CLDAS data can be used to study the characteristics of fogging potential in the Enshi area. (3) There is significant spatio-temporal variation of relative humidity in the Enshi region. The relative humidity in the south region is higher than that in the north, and also varies with the altitude. In terms of time, it increases at night. The relative humidity varies greatly from day to night in the low mountains area, but varies little in the middle mountains area. (4) The spatial distribution and diurnal variation of fogging potential index are basically consistent with that of relative humidity. The highest frequency is found in the southern and central Enshi area between 800 m and 1200 m, and the lowest frequency is found in the northern Three Gorges dry and hot valley, namely the lee side of Wushan Mountains. In addition, the highest frequency occurs in winter.