Based on the NCEP/NCAR reanalysis data and the AWOS data, the weather situation, water vapour conditions and boundary layer structure of two radiation fog processes at Zhaotong Airport on January 3 and December 7, 2019, are compared and analyzed. The commonness and differences of the formation and maintenance conditions of the two radiation fogs are discussed. The results show that: (1) The two fog events both occurred after the rain and snow weather turned clear, and the airport was controlled by the weak pressure field behind the highpressure bottom. However, the water vapour content and dynamic conditions of the “1.3” process were significantly better than those of the “12.7” process, and the fog concentration and duration were both greater than those of the “12.7” process. (2) The process of “1.3” was a typical radiation fog, which formed in the early morning when the weather was clear, the breeze was light, and the radiation temperature droped most strongly. In the process of the fog, if the water vapour was abundant and the dynamic conditions were suitable, it would be conducive to the formation and development of the fog. (3) The radiation fog in the process of 12.7 had the characteristics of local explosive development. Before the burst of the fog, only a light fog formed at the airport due to poor water vapour and dynamic conditions. After sunrise, due to the fog layer in the southwest direction moved northward, the airport’s low temperature and high humidity environmental conditions were conducive to the maintenance of the fog. Moreover, the nearground wind speed was conducive to the mixing of the fog layer, which led to the burst development of the fog in the airport area.