The data of seven parameters AQI, PM2.5, PM10, SO2 , NO2 , CO and O3 from 10 national-controlled automatic air quality monitoring station of Dalian from June to August in 2015 were analyzed to investigate the daily mean change of air quality index, the change of the hour, the special pollution date analysis and the correlation analysis between AQI and other parameters. The results showed that the excellent air quality in Dalian was 44.6%, the standard rate was 97.9% in the summer. The mean change of AQI days was large, and the change trend of AQI wave form was the same from June to August. For the special climate, AQI value maximum was 130.4 in August, and the AQI was significantly decreased due to the rainfall. The regularity of AQI hours from 00:00 to 07:00 when the data changed slowly, the data began to rise in rush hour, and AQI changed between peak and valley. Through correlation calculation, AQI, PM2.5, PM10 were significantly correlated, and CO, NO2 , O3 showed a good correlation with AQI. But the correlation between SO2 and AQI was not obvious, which is the basis for the treatment of air pollution in Dalian.