This study presents one of the first long-term datasets of fine particulate matter (PM2.5) concentrations in 190 Chinese cities, revealing that only 25 cities meet the national ambient air quality standards. The population-weighted mean PM2.5 concentration in Chinese cities is 61 μg/m³, three times the global average, indicating significant health risks. PM2.5 concentrations are generally higher in northern regions due to larger emissions and unfavorable meteorological conditions. Seasonal variability is marked, with the highest levels in winter and lowest in summer. High PM2.5 levels are also observed in spring (Northwest and West Central China) and autumn (East China), attributed to dust and biomass burning. Diurnal variations show peaks in the afternoon, linked to boundary layer depth and emissions. The PM2.5-to-CO ratio peaks in the afternoon, indicating secondary PM formation. Rapid economic growth and urbanization have led to increased haze events, with PM2.5 pollution being a major concern. The Chinese government has implemented new standards, but real-time monitoring is still limited. Satellite data is used to assess spatial distribution. The study highlights the need for improved monitoring and policies to reduce PM2.5 pollution. PM2.5 concentrations vary spatially and seasonally, with the highest levels in the Beijing-Tianjin-Hebei region and the lowest in Hainan. Seasonal variations show higher PM2.5 in winter due to emissions and stagnant weather, while spring and autumn have high levels due to dust and biomass burning. Diurnal patterns show peaks in the afternoon, influenced by meteorological conditions and emissions. The study emphasizes the complexity of PM2.5 formation, involving local and regional emissions, meteorological factors, and secondary production. The results underscore the health risks of PM2.5 pollution and the challenges in meeting air quality targets in China. The study provides insights for developing effective policies to reduce PM2.5 pollution and improve air quality.This study presents one of the first long-term datasets of fine particulate matter (PM2.5) concentrations in 190 Chinese cities, revealing that only 25 cities meet the national ambient air quality standards. The population-weighted mean PM2.5 concentration in Chinese cities is 61 μg/m³, three times the global average, indicating significant health risks. PM2.5 concentrations are generally higher in northern regions due to larger emissions and unfavorable meteorological conditions. Seasonal variability is marked, with the highest levels in winter and lowest in summer. High PM2.5 levels are also observed in spring (Northwest and West Central China) and autumn (East China), attributed to dust and biomass burning. Diurnal variations show peaks in the afternoon, linked to boundary layer depth and emissions. The PM2.5-to-CO ratio peaks in the afternoon, indicating secondary PM formation. Rapid economic growth and urbanization have led to increased haze events, with PM2.5 pollution being a major concern. The Chinese government has implemented new standards, but real-time monitoring is still limited. Satellite data is used to assess spatial distribution. The study highlights the need for improved monitoring and policies to reduce PM2.5 pollution. PM2.5 concentrations vary spatially and seasonally, with the highest levels in the Beijing-Tianjin-Hebei region and the lowest in Hainan. Seasonal variations show higher PM2.5 in winter due to emissions and stagnant weather, while spring and autumn have high levels due to dust and biomass burning. Diurnal patterns show peaks in the afternoon, influenced by meteorological conditions and emissions. The study emphasizes the complexity of PM2.5 formation, involving local and regional emissions, meteorological factors, and secondary production. The results underscore the health risks of PM2.5 pollution and the challenges in meeting air quality targets in China. The study provides insights for developing effective policies to reduce PM2.5 pollution and improve air quality.