•Concentrations of PM and gaseous pollutants in 31 Chinese cities (from 286 sites) were analyzed.•Concentration levels of PMs were significantly different in various cities.•The correlations between PMs and NO2, SO2 were moderate.•The correlation between PMs and CO was instable and that between PMs and O3 was weak. The variations of mass concentrations of PM2.5, PM10, SO2, NO2, CO, and O3 in 31 Chinese provincial capital cities were analyzed based on data from 286 monitoring sites obtained between March 22, 2013 and March 31, 2014. By comparing the pollutant concentrations over this length of time, the characteristics of the monthly variations of mass concentrations of air pollutants were determined. We used the Pearson correlation coefficient to establish the relationship between PM2.5, PM10, and the gas pollutants. The results revealed significant differences in the concentration levels of air pollutants and in the variations between the different cities. The Pearson correlation coefficients between PMs and NO2 and SO2 were either high or moderate (PM2.5 with NO2: r=0.256–0.688, mean r=0.498; PM10 with NO2: r=0.169–0.713, mean r=0.493; PM2.5 with SO2: r=0.232–0.693, mean r=0.449; PM10 with SO2: r=0.131–0.669, mean r=0.403). The correlation between PMs and CO was diverse (PM2.5: r=0.156–0.721, mean r=0.437; PM10: r=0.06–0.67, mean r=0.380). The correlation between PMs and O3 was either weak or uncorrelated (PM2.5: r=−0.35 to 0.089, mean r=−0.164; PM10: r=−0.279 to 0.078, mean r=−0.127), except in Haikou (PM2.5: r=0.500; PM10: r=0.509).