Abstract: Based on hourly observational data, hourly Air Quality Index (AQI) monitoring values, and ERA5 reanalysis data of 10-meter wind speed and direction from January 2019, a heavy pollution weather process in Yibin was analyzed. The results show that the heavy pollution was primarily caused by the accumulation of pollutants due to the formation of a wind speed stagnation zone in Yibin. The wind speed stagnation zone began to form at 18:00 and eventually developed into an arc-shaped zone extending from Ya'an to Yibin and further to Luzhou during the night. During this pollution process, the primary pollutants in Yibin were PM_2.5, PM₁₀, and NO₂. The pollution was the most severe at No. 4 Middle School Station and Shima Middle School Station, and the lightest at the Shaping Middle School Station. The types of pollutants and the proportional distribution of each pollutant were similar in Yibin and the surrounding cities, suggesting the possibility of regional transport.