The　detection　of　emerging　contaminants　(ECs)　and　understanding　their　ecotoxicity　has　brought　new　challenges　to　water　pollution　control.　Triclosan　(TCS),　as　an　emerging　contaminant,　is　a　commonly　used　antibacterial　agent　widely　present　in　the　environment.　Microdialysis　(MD),　as　a　sampling　technique,　can　overcome　some　of　the　deficiencies　of　traditional　approaches　to　sampling,　using　sources　such　as　blood,　urine,　tissue,　and　target　organs,　in　terms　of　invasiveness,　time　from　collection　to　analysis,　and　possible　changes　during　sample　preparation.　In　this　study,　we　coupled　MD　with　analysis　using　UHPLC-QTOF/MS　to　identify　the　endogenous　metabolites　in　the　liver　as　biomarkers　of　the　exposure　of　living　crucian　carp　to　TCS.　The　identified　biomarkers　were　then　quantified　using　UHPLC-MS/MS　to　continuously　monitor　the　effect　of　TCS　on　endogenous　metabolites　in　the　liver　of　living　crucian　carp,　which　contributes　to　a　better　understanding　of　the　toxicological　effect　of　TCS.　The　experimental　results　demonstrated　that　TCS　exposure　interfered　with　the　metabolic　pathways　of　amino　acids　(l-isoleucine　and　l-histidine),　purines　(xanthine　and　hypoxanthine),　and　small　nerve　molecules　(acetylcholine　and　choline).