Abstract: Water quality criteria for per- and polyfluoroalkyl substances (PFAS) are still lacking in China. This study collected acute and chronic aquatic toxicity data for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and derived ecological thresholds for seawater and freshwater using species sensitivity distribution (SSD) method. The long-term thresholds for PFOA and PFOS were determined to be 0.425 μg/L and 3.472 μg/L in seawater, respectively, and 13.43 μg/L and 1.822 μg/L in freshwater, respectively. This suggests that PFOA is more toxic to marine species, while compared to marine species, freshwater species like water flea (Daphnia carinata) may be more sensitive to PFOS. Risk assessment based on the derived thresholds indicated moderate potential risk for PFOA in Laizhou Bay, Bohai, while no obvious ecological risk was found for PFOS in major coastal waters of China. These findings may support the development of PFAS water quality criteria and the establishment of relevant pollution control regulations.