Abstract: Based on the observation data of fog days, average temperature, minimum temperature, and relative humidity of 14 national observation stations in Chengdu from 1980 to 2021, combined with environmental monitoring data and population data such as PM_2.5, PM₁₀, NO₂ and SO₂, the climate characteristics of fog in Chengdu and its relationship with urbanization process and air quality are analyzed. The results show that the climate distribution of foggy days in Chengdu area shows the regional characteristics of the most in the center, followed by the east and the least in the northwest. The most is in winter, followed by autumn, the least in summer. The foggy days in Chengdu shows a decresasing trend, and the annual change rate of fog days in the central region is larger. The number of fog days is closely related to relative humidity, temperature, and urbanization progress. The development and changes of Chengdu have led to the difference of fog mutation years in different regions. The development of the west is earlier than that of the east, so the fog mutation year in the west was earlier than that of the east. Under the influence of heavy fog, the pollution of PM_2.5 is more likely to occur in Chengdu area. In recent years, the more fog days in Chengdu area, the greater concentration of air pollutants, sepecially the most significant increase of PM_2.5 concentration.