Moutai Airport in Guizhou Province is a typical highland mountain airport, where foggy weather always threatens the safe operation of the airport and is difficult to forecast. This article explores the influence of quasi-stationary front oscillations on foggy weather through a comprehensive analysis of a foggy weather process at Moutai Airport in autumn, with a view to deepen the understanding of the foggy weather formation mechanism. Using the observation data at Moutai Airport on October 16, 2019 and ERA5 hourly reanalysis data (0.25° × 0.25°) as well as the methods of weather science analysis, diagnostic analysis, and HYSPLIT water vapor tracking, we analyze the formation mechanism of foggy weather in highland mountain airports, and explore the influence characteristics of the quasi-stationary fronts on heavy fog. The results show that the heavy fog process occurred during the oscillation of the quasi-stationary front from north to south in Yunnan and Guizhou. During the fog period, the large-scale circulation was very stable, with a blocking situation at mid-latitudes at 500 hPa and a deformation field at 700 hPa. This was conducive to the strengthening and maintenance of the quasi-stationary front. The heavy fog was divided into two stages: the first part of fog appeared when the surface quasi-stationary front was in transit, but the low-level frontal area had not yet arrived at Moutai Airport. At this time, the airport ground had been affected by cold advection, and the lower level was still under the control of warm advection. Thus, the southwest warm and humid airflow got cooled in the cold underlying surface, forming heavy frontal fog. After the quasi-stationary frontal area gradually left the airport from north to south, visibility improved as the result of the weakening of the frontal effect. The second stage of heavy fog occurred in the cold air mass on the north side of the quasi-stationary front. At this time, water vapor from the Chishui River Valley in the northwest got cooled at the airport and formed fog. The inversion over the airport increased the stability of the atmospheric stratification, which was favorable for the maintenance of the foggy weather. HYSPLIT water vapor tracking shows that the low-level water vapor was mainly from the Bay of Bengal and the Chishui River Valley, while the mid-level water value was from the Bay of Bengal. The further southward moving of the quasi-stationary front and the warming effect of the ground after daybreak jointly improved the vertical diffusion conditions over the airport, then the fog gradually dissipated. In a word, oscillations of quasi-stationary fronts altered the characteristics of the wind field, stratification stability, temperature advection and water vapor sources in the vicinity of the airport, which in turn affected the onset, maintenance, and dissipation of the heavy fog.