Abstract: At present, there are four relatively serious haze areas in China, which are the areas of Beijing, Tianjin and Hebei, the Yangtze River Delta, the Pearl River Delta and the Sichuan Chongqing area, and Zigong is the most severe haze area in Sichuan. It is necessary to study the causes of the high haze in Zigong. Based on the Zigong ground observation data from 2005 to 2016 and taking the sustained haze weather process from December 21, 2017 to January 3, 2018 as an example, with the help of air quality data, ground meteorological elements and high altitude observation data, analysis of the relationship between terrain, meteorological factors and environmental pollution. The results show when Zigong is an easterly or northward air flow, the pollutant is easily converged in the plain area in the front of the mountain under the wind transmission. In addition, it is easy to form a cyclone flow field in the southern part of the Sichuan basin, which makes it difficult to spread and transport the air pollutants in a long distance and form a vortex. Zigong is located in the central area of pollutant retention, causing the accumulation of pollutants in the urban area and the increase of concentration. Zigong is limited by its own geographical location and natural climate characteristics, the weather conditions are deficient, the air environment carrying capacity is low, the air self purification ability is not strong, and haze is easy to appear.