Abstract: To provide reliable data and reference for the improvement of water quality in Jiaxing city, the water monitoring and evaluation was conducted. Based on the monitoring data of the monitored sections in the city in 2020, the proportion of water quality, the concentration of the main pollutants, over-standard rate of water quality,pollution sharing rate and 21 comprehensive pollution indexes were analyzed. The results showed that the total phosphorus, dissolved oxygen and ammonia nitrogen were the main items exceeding class Ⅲ standard in 2020.Total phosphorus had the highest sharing rate. The surface water quality in Jiaxing city was generally excellent,and the water quality was improved clearly than last year.