Abstract: Polycyclic aromatic hydrocarbons (PAHs) are a type of typical persistent organic matters, which are widely distributed in China's water body. Ecological risk assessment of PAHs is now a hot issue and is of great significance to the management and protection of aquatic ecosystems. At present, the aquatic ecological risk assessment of PAHs is mainly focused on individual and population level, and there is still a lack of ecosystem level studies. Based on the Ecotoxicology Database of United States Environmental Protection Agency (ECOTOX), this paper obtains reliable acute and chronic toxicity data of species according to the trophic functional group classification of aquatic ecosystems, and develops the species sensitivity distribution (SSD) curves of eight common PAHs such as naphthalene, aenaphthene, fluorene, anthracene, pyrene, phenanthrene, fluoranthene and benzopyrene, using Burr Ⅲ distribution fitting curve. Combined with the acute and chronic data ratio method, the baseline values of chronic toxicological water quality based on ecosystem level are derived, which are 10.25, 6.75, 0.06, 1.95, 0.03, 3.50, 0.05, 0.50 μg·L-1 respectively. These results are close to the values of existing standards at home and abroad, which verifies the reliability and accuracy of the results. The developed method is applied for the ecological risk assessment of PAHs in the seven major river basins of Songhua River, Liaohe River, Haihe River, Yellow River, Yangtze River, Huaihe River and Pearl River. It is found that the risk of the Haihe River and the Yangtze River is low; the risk of the Yellow River, the Huaihe River and the Pearl River is moderate; the risk of the Songhua River and the Liaohe River is the highest. The method developed in this paper provides a reference for the establishment of water quality benchmarks for PAHs and similar pollutants, as well as for ecological risk assessment at the ecosystem level.