Abstract: According to the data of various indicators of water quality in the Suzhou section of Yangtze River from 2019 to 2022, the change trend was analyzed. The results showed that the water quality in July of the whole year was the worst, with ammonia nitrogen and dissolved oxygen being the main indices exceeding the standard. The water quality in summer was slightly worse than other seasons, and the main index exceeding the standard was dissolved oxygen. The water quality in 2022 was better than the previous years, and the proportion of Class Ⅱ water sections had increased, the number of substandard months had decreased, and the rate of measurement times was concentrated at more than 90%. Dissolved oxygen, total phosphorus and total nitrogen showed obvious seasonal variation. The contents of dissolved oxygen and total nitrogen were higher in winter and spring and lower in summer and autumn. On the contrary, the concentration of total phosphorus was lower in winter and spring and higher in summer and autumn. The water diversion project of Qiputang improved the water quality in the surrounding areas obviously. The dissolved oxygen, ammonia nitrogen and total phosphorus in the water diversion period of Qiputang and Lake Yangcheng were significantly better than those in the drainage period.