Abstract: The accumulation of PFOS (perfluorooctane sulfonate) in sediments has a potential hazard to the aquatic ecosystem. In order to evaluate the adverse effects of PFOS in sediments, the toxic effects of PFOS in sediments on benthic organisms, including Chironomus kiiensis, Hyalella azteca and Limnodrilus hoffmeisteri, were investigated using mortality and growth-inhibition as toxic endpoints. Based on the results of toxicity experiments and collected toxicity data from the references, the sediment quality criteria (SQC) of PFOS was derived by species sensitivity distributions (SSD). Based on the obtained SQCs of PFOS, the ecological risk of PFOS in the sediments of seven major river systems in China was evaluated. The results showed that:(1) The toxic effect of PFOS on Chironomus kiiensis was the most significant, and the LC₅₀ values were 0.894, 0.770 and 0.536 μg/g for the 96 h, 10 d and 21 d toxicity tests, respectively. No death was observed in the 10 d toxicity test (maximum concentration 156.5 μg/g) of the Hyalella azteca, while the LC₅₀ was 70.5 μg/g in the 21 d toxicity test. As Limnodrilus hoffmeisteri was used, no significant death occurred in the 10 d toxicity test (maximum concentration 112.4 μg/g) and 21 d toxicity test (maximum concentration 76.4 μg/g). (2) The CMC_sed was 28.6 μg/g and the CCC_sed was 0.060 μg/g. (3) The w(PFOS) was lower than CCC_sed in the sediments of 96% of China's seven major river systems, while the w(PFOS) was higher than CCC_sed but lower than CMC_sed in other sediments, which was mainly distributed in the middle and lower reaches of the Yellow River and the lower reaches of the Yangtze River. In conclusion, the overall risk of PFOS in the sediments of the seven major river systems in China is relatively low, but the PFOS in the sediments of the middle and lower reaches of the Yellow River and the lower reaches of the Yangtze River may have potential risks and need more attention.