Abstract: Based on the air quality and socio-economic data of 31 provincial capital cities,the present situation of urban air quality and its social and economic influencing factors were analyzed by the extensible random environmental impact assessment model(STIRPAT model). The results showed that the annual mean value of AQI implied a linear downward trend,while the monthly mean value curved a U-shaped from 2013 to 2017. Those cities with poor air quality are mainly located in North China,East China,Central China and Northwest China. The sample cities could be divided into three grades according to their air quality. Technology and industrial structure factors had a significant impact on urban air quality,while population,wealth,transportation,greening and other factors had no significant impact on air quality. Some policy suggestions were put forward to improve urban air quality.