We presented the characteristics of PM_2.5 chemical composition over China during 2005–2012 by synthesis of in situ measurement data and satellite-based estimates. We also investigated the driving forces behind the changes by examining the changes in precursor emissions. We found that the decrease in sulfate is partly offset by the increase in nitrate. The results indicate that the synchronized abatement of emissions for multipollutants is necessary for reducing ambient PM_2.5 over China.