In order to study the atmospheric environment changes and main influencing factors in Guiyang City over the past decade, utilizing the data in the last ten years in Guiyang and during the pollution emission gap for COVID_19 pandemic control in September 2022, we comprehensively analyze the atmospheric environment in Guiyang from the aspects of the Air Quality Index (AQI), pollutant concentrations, meteorological conditions, acid rain, and backward trajectories. It is found that over the past decade, the AQI in Guiyang has shown a significant overall downward trend, with the air quality level improving from " moderate " to " good ". However, during the pandemic period after 2020, the AQI increased unexpectedly instead of decreasing. The concentrations of SO2, NO2, PM10, PM2. 5, and CO have shown a decreasing trend year by year, while the concentration of O3 increased from 68. 5 μg/m3 in 2014 to 78. 5 μg/m3 in 2023. Notably, it even increased to 90 μg/m3 in September 2022 during the static management period of the pandemic. Among all pollutants, only O3 showed a significant positive correlation with temperature and radiation, and their correlation coefficients are 0. 6 and 0. 64, respectively. This indicates that the source of O3 was not from industrial or transportation emissions, but rather dominated by meteorological conditions. The acid rain in Guiyang showed an overall gradual improvement from 2008 to 2017, characterized by a decrease in acid rain frequency and an increase in precipitation pH value. However, from 2017 to 2023, the acid rain frequency increased, while the precipitation pH value decreased. The highest seasonal average precipitation pH value (pH = 5. 52) occurred in summer, while the lowest (pH = 4. 80) was in winter. Backward trajectory analysis shows that during the pandemic period in September 2022, the relatively short_range airflow transport was not conducive to the pollutant dispersion, which may have been the main reason of the high particulate matter concentrations during this period. Generally, over the past decade, concentrations of traditional pollutants in Guiyang have continued to decline, but the current challenge in air quality has shifted to O3 pollution and acid rain issues caused by complex meteorological conditions in mountainous areas, so it is urgent to formulate coordinated control strategies.