Abstract: Based on field investigation and literature survey,the species composition,geographical elements,and endangered state of aquatic vascular plants in the Yangtze Delta were analyzed.We found 185 wild species belonging to 90 genera and 39 families in this area,most of which were distributed in habitats such as ditches, rice-fields, and ponds.Additionally,emergent plants were the main type in terms of life form.This flora was chiefly temperate in nature according to areal-type analysis both at the level of genera and of species.In light of IUCN Red List Categories and Criteria (Edition 3.1),those species were classified into 9 types, including Regionally Extinct (RE) 1,Critically Endangered (CR) 3,Endangered (EN) 8,and Vulnerable (VU) 10.Finally,we also examined the main reasons causing these aquatic plants to become threatened.