To study the characteristics of air pollution in Nanjing during the summer, an intensive observational experiment was carried out from August 15th to September 15th, 2016. Data from three sites (Xianlin, Caochangmen, and Gulou) were collected to analyze the characteristics and correlation between O₃ and particulate matter (PM_2.5, PM₁₀) concentrations. Xianlin, Caochangmen, and Gulou each represented suburban, urban, and urban upper air respectively. In addition, at the Xianlin site, conversion characteristics of water-soluble ions and their gaseous precursors were also analyzed. The study showed that the hourly average concentration of O₃ was 100.3μg/m³. Average hourly concentrations of PM_2.5 and PM₁₀ were 41.1μg/m³ and 67.8μg/m³, respectively, and a peak was observed during the nights at the suburban site. The sum of the SO₄^2-, NO₃^- and NH₄⁺ to PM_2.5 ratios reached 0.61 and the OC (organic carbon) to EC (elemental carbon) ratio ranged from 0.8 to 4.0, with 77% of the days being greater than 2.0. The high OC/EC ratio indicated the existence of secondary pollution. The correlation between O₃ and PM concentrations was significantly positive, especially at the daytime. Similarly, the conversion rate of sulfur (SOR) and nitrogen (NOR) was correlated with daylight O₃ and nighttime humidity, respectively. Also, the accumulation of HONO mainly occurred during the night, while that of HCl and HNO₃ occurred in the afternoon. Compared with other inorganic salts, the ratio of NH₄⁺ in total ammonia was quite small, which showed that gaseous NH₃ was the main phase state. In conclusion, the potentially important role of chemical reactions in the accumulation of PM_2.5, especially involving secondary particles, and transport of air pollution from urban to suburban is addressed.