In this paper, spatial-temporal features of the air quality index (AQI) in Yangtze River economic belt were studied by the real-time monitoring data on air quality from 2015 to 2018, and emissions of air pollutants and meteorological factors were taken as two evaluating indicators to reveal the factors and their seasonal variation to the distribution of AQI in the target regions by geographical detector. The air quality of Yangtze River economic belt was improving from 2015 to 2018 with an average ratio of days beyond standard decreased to 16.2% from 19.8%, and the rest of monitoring indicators were decreasing more or less except a rising ratio of days beyond standard for O₃. In terms of the ratio of days beyond standard, PM₁₀ was overtook by O₃ and became the second most significant pollutant following PM_2.5 for Yangtze River economic belt since 2017. The monthly variation curve for AQI showed a "U" model, which was higher in winter and spring and lower in summer and autumn. The improving mentioned was particularly witnessed in winter and autumn. And the rising concentration of O₃ then led to a rising ratio of days beyond standard in summer, but a minus variation was seen in spring. AQI and ratio of days beyond standard presented a pattern of being higher in the east and north, and lower in the west and south. And the most polluted area covered Shanghai, Jiangsu, central and northern Anhui, and northern Zhejiang, then followed by central Hubei and Chengdu-Chongqing area, and the air quality was good in Yunnan, Guizhou, and western Sichuan. The variation of AQI in spring and summer was mainly presented when studied on east-west direction while it turned to south-north direction in autumn and winter. Factors to emissions of pollutants had a positive influence on the distribution of AQI in target areas, while there was a seasonal variation when it came to the direction of the influence by meteorological factors. The distribution of AQI in the whole year, spring, autumn and winter was mainly determined by the emission factors of air pollutants, while a more powerful influence was seen by meteorological factors in summer. Factors to emissions of pollutants had a positive influence on the distribution of AQI in target areas, while there was a seasonal variation when it came to the direction of the influence by meteorological factors. Whether for the whole year, spring, autumn or winter, the distribution of AQI was decided by the volume of air pollution pollutant, and a more powerful influence was seen by meteorological factors in summer.