To study the water ecoenvironment quality of seagoing rivers in Yancheng， a survey on periphytic algae community structure in main seagoing rivers of Yancheng was conducted in May and September 2022， and the water ecology of 10 seagoing rivers were evaluated based on rivers water eco-environment quality comprehensive evaluation index. The results showed that the proportion of sections with good-quality surface water reaching Grade III and above was 70% throughout the year， and the permanganate index and dissolved oxygen were the main influencing factors on the water quality of the section. Shannon-Wiener index（H′）was between 2.77~4.4， with a mean value at 3.97. The overall evaluation level was excellent. The survey found that there were 7 phylum of periphytic algae， including diatoms， green algae， cyanobacteria， euglenophyta， dinoflagellates， cryptophytes， and xanthophyta， a total of 129 species； 88 species（genera） were found in May， and 95 species（genera） were found in September. Diatom dominated the community all over the year. 80% of the total sections were good or above according to ecoenvironment quality comprehensive evaluation index， water quality and habitat were the main factor constraining the water ecoenvironment quality comprehensive evaluation index of seagoing rivers.