Due　to　their　widespread　use　and　harmful　effects　on　aquatic　environment,　sulfonamide　antibiotics　(SAs)　have　become　an　emerging　pollutant　of　great　concern　around　the　world.　In　this　study,　we　investigated　the　degradation　process　and　mechanism　of　sulfamerazine　(SMR),　sulfadiazine　(SDZ),　and　sulfapyridine　(SPD)　by　electron-beam　irradiation　(EBI).　The　results　showed　that　the　three　SAs　were　well　suited　to　the　pseudo-first-order　reaction　kinetics,　and　they　could　be　almost　completely　removed　with　high　efficiency　(5　kGy).　Among　the　environmental　factors,　pH　(3.0)　and　O-2　atmosphere　can　further　enhance　the　removal　of　the　sulfonamides　(SAs),　while　NO2-　has　the　most　pronounced　degrading　inhibitory　effects　among　the　many　ions,　these　results　illustrate　that　hydroxyl　radicals　play　a　dominant　role.　Compared　with　SMR　and　SDZ,　the　degree　of　mineralization　of　lower　molecular　weight　SPD　is　obvious　(45%).　LC-MS　and　DFT　calculations　indicate　that　the　concentrations　of　degradation　products　of　the　three　SAs　show　a　tendency　to　increase　and　then　decrease,　demonstrating　that　EBI　can　achieve　efficient　removal　and　further　mineralization　of　SAs.　Meanwhile,　the　results　of　the　common　product　4-Aminophenol　produced　during　the　degradation　process　further　indicate　that　HO　center　dot　is　the　predominant　reactive　oxygen　species　(ROS).　In　addition,　acute　toxicity　experiments　with　luminescent　bacteria　and　predictions　of　ECOSAR　procedures　proved　the　toxic　effects　greatly　decreased　after　the　degradation.　This　study　provides　new　ideas　for　achieving　efficient　and　profound　removal　of　emerging　pollutants　from　the　aquatic　environment.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.