Abstract: Water quality criteria (WQC) is the scientific basis for formulating water quality standards (WQS), and the ecotoxicological data is the basis of WQC. Therefore, the quality of ecotoxicological data must be evaluated before deriving WQC. Using the data quality evaluation methods of the United States, the European Union, Australia and New Zealand for reference, the method of ecotoxicological data quality assessment for WQC establishment in China was proposed. The method was established from the following 5 aspects, 25 items with a total score of 100, including data sources, chemical substances, test organisms, experimental process and experimental results. For each kind of ecotoxicological data, the quality was graded according to its final score. The principles of quality assessment were as follows: score≥80, high quality data; 60≤score<80, acceptable data;score<60, unacceptable data. In the process of evaluation, when the individual evaluation result was invalid, the evaluation process must be terminated directly. The evaluation method of ecotoxicological data developed in this study would further enriched the technical method of WQC establishment in China.