Abstract: Based on data at 405 ambient air quality assessment sites, air quality data and conventionally-observed meteorological data in Wuhan city during 100°-120°E, 25°-45°N from 2013 to 2017, the trigger mechanism and main factors of urban heavy pollution processes in Wuhan are analyzed by weather and mathematical statistics methods. The result shows that:(1) The frequency and the average duration of the process of air quality heavy pollution in Wuhan are obviously decreasing. (2) The weather situation that causes the heavy pollution of air quality in Wuhan city is cold air invasion and statically stable weather. The formation mechanism is caused by the increase of wind speed, which leads to the transport of pollutants in the upper AQI area of the upstream of the wind direction, and the poor diffusion conditions lead to the accumulation of local pollutants. (3) The typical weather model for the heavy pollution process in Wuhan city is:The accumulation of local pollutants at the beginning of the process, the increase of wind speed leading to the input of exogenous pollutants, and superposition of internal and external pollutants after cold front transit. The condition improves due to diffusion and the process is then over. (4) The relationship between air quality and meteorological elements, such as atmospheric pressure, wind, temperature, is often characterized differently depending on weather conditions. Under different weather conditions, the trend of AQI should be analyzed based on real-time variation of air pressure and the characteristics of temperature and wind.