Abstract: To investigate the impact of eutrophication on aquatic and riparian plants in the Tumen River Basin, 354 sampling sites were established from 2020 to 2023 for systematic vegetation surveys and biodiversity analysis. A total of 143 aquatic plant species (including 17 invasive species) and 510 riparian species (including 8 invasive) were documented, along with 5 Class II nationally protected plants. Based on the Trophic Level Index (TLI), eutrophication severity was ranked as follows: Burhatong River (65.8) >Gaya River (59.7) >Tumen River mainstem (54.4) >Hailan River (54.5) >tributaries (28.4). Diversity indices responded nonlinearly to eutrophication: Shannon and Simpson indices followed unimodal patterns, while Margalef richness and the Cody index declined significantly (P<0.05). Notably, the contribution of species turnover to β diversity increased from 32% to 58%. These findings provide valuable theoretical insights for the conservation and sustainable utilization of aquatic-riparian plant resources, as well as for invasive species management in the Tumen River basin.