Abstract: Base on the air quality monitoring data, upper-air and surface meteorological observation data, NCEP reanalysis data, we analyzed the heavy pollution weather process characteristics and meteorological conditions during the new year's day of 2016 in Dazhou City. The results show that: The heavy pollution weather process in Dazhou city was a long time without cold air activity, no rain and the accumulation of atmospheric pollutants. AQI diurnal change was affected by the emissions of pollution more than weather conditions, low in the morning, gradually increased during the day, reached the peak after dark.The accumulation of atmospheric pollutants generally occurred at a neutral or higher level of atmospheric stability. AQI was negatively correlated with the thickness of atmospheric mixed layer at 8 and 17, but the average thickness of atmospheric mixed layer and AQI did not pass the correlation test. When AQI was heavy pollution, there was temperature inversion layer near the ground and the inversion layer was thick. AQI was positively correlated with daily maximum temperature, daily mean wind speed and daily maximum wind speed. The effect of rainfall on the dilution of atmospheric pollutants was obvious, and the longer rainfall time, the larger precipitation, the effect is more significant. AQI hourly variation is positively correlated with temperature and negatively correlated with wind speed.