Abstract: Quaternary ammonium compounds (QACs) are cationic surfactants containing hydrophobic hydrocarbon chains that are widely used as broad-spectrum, highly effective disinfectants in cleaning and disinfection products. They have been detected in various surface water bodies globally. To scientifically assess the potential risks of QACs to aquatic ecosystems, this study systematically reviews the current status of water quality criteria and ecological risk assessment research, analyzing existing problems and challenges. Through a literature review, we systematically examined the pollution characteristics, toxic effects, and mechanisms of QACs, and comparatively analyzed different countries' research progress and technical methods in criteria derivation and risk assessment. The results show that: (1) Only the United States and Canada have derived water quality criteria for Didecyl Dimethyl Ammonium Chloride (DDACs), while other countries have not yet conducted related research. (2) QACs can cause multiple effects on aquatic organisms even at environmentally relevant concentrations, including endocrine disruption, reproductive inhibition, and neurotoxicity, with long-chain QACs such as hexadecyl dimethyl benzyl ammonium chloride (BAC-C16) typically exhibiting stronger toxicity. (3) Water quality criteria research for QACs faces challenges including complex homolog varieties, insufficient basic toxicity data, and limited derivation method options. (4) There is a notable lack of environmental monitoring data for QACs globally, especially exposure data since the coronavirus disease 2019, which constrains effective ecological risk assessment. It is recommended to strengthen research on the relationship between molecular structure and toxicity of QACs, improve the classification evaluation system for different homologs, innovate criteria derivation methods considering structural correlations, enhance environmental monitoring data, and promote international cooperation and data sharing, thereby providing scientific basis for continuous improvement of water environmental quality.