Abstract: Potassium ferrate has been widely used as a water quality improver in aquatic industry, but the safety of its use and the reference value of freshwater aquaculture organisms have been unclear. In this study, the species sensitivity distribution (SSD) method was used to determine the reference value of potassium ferrate and evaluate the ecological risk of potassium ferrate to freshwater aquaculture organisms. The acute toxicity of potassium ferrate to 14 freshwater aquatic organisms was obtained by acute toxicity test. Six fitting models were selected to fit the toxicity data, and the regression coefficient and residual sum of squares were compared to determine the model with the best goodness of fit. The HC₅ threshold (hazardous concentration for 5% of the species) of potassium ferrate for different species and the reference value of potassium ferrate for freshwater aquaculture organisms and freshwater aquatic organism were derived. The potentially affected fraction (PAF) of potassium ferrate on freshwater aquaculture organisms was calculated by using the SSD model. The results show that: (1) The sigmoid model had the best goodness of fit, and the basic safety value of potassium ferrate for all freshwater aquatic organisms was 6.82 mg·L^-1, and for freshwater aquaculture organisms was 9.53 mg·L^-1. (2) The PAF value corresponding to the concentration value of potassium ferrate used in daily aquaculture is 0, indicating low ecological risk. The results can provide scientific basis and theoretical guidance for the formulation of reference value of potassium ferrate in freshwater aquaculture organisms and the safe use of potassium ferrate.