Fluoxetine　(FLU),　a　selective　serotonin　reuptake　inhibitor,　is　commonly　found　in　aquatic　environments.　Ultraviolet　(UV)　photolysis　is　widely　used　to　remove　certain　pharmaceuticals　from　water　and　wastewater.　The　present　study　aimed　to　investigate　the　toxicity　of　FLU　and　its　transformed　products　formed　during　UV　photolysis　by　using　zebrafish　embryos　(Danio　rerio)　as　a　model.　The　degradation　rates　of　FLU　for　five　days　were　approximately　63.6%　+/-　2.14%,　84.6%　+/-　0.99%,　and　97.5%　+/-　0.25%　after　15,　30,　and　60　min　of　UV　irradiation,　respectively.　Furthermore,　the　degradation　mechanism　was　explored　using　LC-MS　measurements　and　density　flooding　theory　(DFT)　theoretical　calculations.　Comprehensive　toxicity　preassessment　of　FLU　and　its　degradation　products　was　carried　out　using　the　T.E.S.T.　software.　The　effects　of　physiological　and　biochemical　parameters　and　neuron-and　apoptosis-related　gene　expression　were　examined　in　zebrafish　embryos　exposed　to　non-irradiated　(0-min)　and　irradiated　(15,　30-and　60-min)　solutions　from　4　h　post-fertilization　(hpf)　to　120　hpf.　The　hatching　time　of　zebrafish　embryos　exposed　to　the　non-irradiated　solution　(0-min)　and　irradiated　solution　(60-min)　was　delayed,　their　heart　rate　at　48　and　72　hpf　increased,　and　their　body　length　at　120　hpf　decreased.　Significant　differences　were　found　between　the　non-irradiated　(0-min)　and　UV-irradiated　(15-or　30-min)　groups.　A　dynamic　response　involving　acetylcholinesterase　(AChE)　and　superoxide　dismutase　(SOD)　activity　was　also　observed　in　the　non　irradiated　and　UV-irradiated　groups.　During　the　UV　treatment　experiments,　the　expression　levels　of　neuron　related　and　apoptosis-related　genes　were　significantly　reduced　over　time　alongside　the　formation　of　FLU　degradation　products.　Overall,　this　study　provides　new　concepts　to　remove　and　assess　the　toxicity　of　emerging　contaminants　in　aquatic　environments　and　highlights　the　need　to　consider　the　formation　and　persistence　of　toxic　transformation　products.