Abstract: Based on "Ambient air quality standards"(GB3095-2012) and the daily air quality index (AQI) from Jan. 21 to Mar. 25 of 2020 being in the strict period of COVID-19 pneumonia contagion prevention and control in the central city of Xinyang of Henan province,China, the daily changes of ambient air quality was investigated. The results showed:there was no severe air pollution day occurred except 11 light, 3 middle and 1 heavy pollution days, which indicated that the ambient air quality in this city in this period was greatly improved and became the best compared with the same historical period since 2016. However, ambient air quality showed its temporal oscillation. Pollution days in this period happened easily under weather conditions such as cloudy, overcast sky, drizzle, flurry and the north or northerly wind not higher than breeze but carrying air particle pollutants. Particulates, PM_2.5 in particular, were the primary air pollutants, and ozone still showed its potential pollution in this period as before.The contagion prevention and control measures had an significant influence on the air quality, and neither middle nor heavy pollution day occurred under stringent measures, but a few light pollution days happened as well. All the above suggest that the particle pollutants, especially PM_2.5, as well as O₃ might be the formidable challenges in the future to this city or even the akin cities in China being dedicated to a better ambient air quality.