Abstract: Using the conventional observation data including ground visibility, relative humidity, temperature, and wind speed obtained from the observation of Liupan Mountain, Jingyuan, and Longde meteorological stations in 2020, along with vertical observation data of temperature and humidity of microwave radiometers, the circulation pattern and vertical evolution characteristics of temperature and humidity during the fog events occurring on the eastern slope and the mountaintop, as well as only on the eastern slope were analyzed. The results indicate that during the two fog events, the the Eurasian region was under the circulation background of two troughs and one ridge, with significant warm advection in the upper level and cold advection in the middle level. The fog process on the summit and eastern slope was a systematic cloud and fog precipitation weather process, while the fog process on the eastern slope was a local fog process caused by the warm and humid air flow from the south in combination with the terrain. During the two fog events, the ground relative humidity exceeded 90%, and the relative humidity was basically maintained at 99% during the fog persistence. The wind speed on the summit was relatively high, while the wind speed on the eastern slope was lower. During the systematic cloud and fog precipitation process (on the summit and eastern slope), the southwest wind dominated on the summit, while the wind direction on the eastern slope fluctuated significantly due to the influence of terrain. During the fog process on the summit, the relative humidity and the top of the temperature inversion layer showed upward extension, and the bottom of the inversion layer extended upward with the weakening of the fog.