The acute toxicity data of Cr6+ and Hg2+ to the aquatic organisms in Liaohe River basin was collected and screened. Calculated results of criteria values of international species sensitivity distribution (SSD) methods were evaluated through data analysis. The comprehensive methodologies of emergency water quality standard (WQS) were established based on the SSD method of Australia and New Zealand according to the evaluation results. The affected fractions of the aquatic organisms was set to be 5 %, 15 %, 30 % and 50 %, corresponding to the risk grades of I, II, III and IV, and four-grade emergency WQS, respectively. The emergency WQS for Cr6+ and Hg2+ in the Liao River basin were derived and the corresponding risk indicators were also proposed. The results showed that the four-grade emergency WQSs for Cr6+ were 2.85 μg/L, 21.0 μg/L, 161 μg/L and 797 μg/L, respectively, and the risk indicators were daphnia (grade II), shrimp (grade III), and the bighead fish or tadpole (grade IV). The four-grade emergency WQSs for Hg2+ were 0.59 μg/L, 2.32 μg/L, 6.25 μg/L and 15.6 μg/L, respectively, and the risk indicators were crucian carp or daphnia (grade II), shrimp (grade III), and worm or crab (grade IV). The results provide valuable information for the risk analysis of emergency ambient water environmental pollution accident.