The data of AQI from 10 countries accused of automatic air quality monitoring station of Dalian from June 2015 to December 2016 were analyzed to investigate the daily mean change of air quality index, the change of the hour and the correlation analysis between AQI and PM2.5, PM10, SO2, NO2, CO, O3 six parameters. The 856,800 index samples showed that the air quality index of autumn and winter was obviously higher than that of summer. The maximum AQI value in autumn and winter reached 389, with an average of 82. The maximum value of AQI in summer was 130, and the average was 50. From 2015 to 2016, the excellent air quality in the summer in Dalian was 60.3%; the standard rate was 98.4%. The autumn and winter air quality accounted for 39.1% and the compliance rate was 68.5%. The mean of the AQI average daily was a wavy trend, and the changes of summer and autumn and winter were roughly the same. The regularity of AQI 24-hour showed multi-peak changes, bimodal changes and single peak changes. The air quality in Dalian is affected by the weather conditions such as wind direction, rainfall and fog, the air quality in surrounding cities, urban pollution, vehicle exhaust and excessive consumption of coal energy. Through correlation calculation, AQI, PM2.5, and PM10 were significantly correlated irrespective of season. AQI and O3 were positively correlated in summer, but negatively correlated in autumn and winter, which is the basis for the treatment of air pollution in Dalian.