The　degradation　kinetics　and　primary　radiolytic　degradation　mechanism　of　diethylstilbestrol　by　electron　beam　irradiation　have　been　investigated.　The　results　show　that　the　electron　beam　irradiation　is　an　effective　method　to　reduce　diethylstilbestrol.　The　degradation　of　diethylstilbestrol　in　acetonitrile/water　oxidative　system　is　higher　than　in　methanol/water　reductive　system　at　the　same　absorbed　dose.　Furthermore,　the　study　indicates　that　the　decomposition　rate　increased　with　the　addition　of　H2O2　to　the　solution.　These　illustrate　hydroxyl　radical　(center　dot　OH)　might　play　a　crucial　role　in　degradation　of　diethylstilbestrol.　The　removal　of　diethylstilbestrol　followed　pseudo-first-order　kinetic　in　acetonitrile/water　solution　and　the　kinetics　rate　constant　decayed　exponentially　with　increasing　initial　concentration　of　diethylstilbestrol.　The　degradation　rate　of　diethylstilbestrol　decreased　with　increasing　absorbed　dose　in　acetonitrile/water　solution,　which　was　illustrated　by　changes　in　specific　reduction　efficiency　and　increased　with　decreasing　initial　concentration　at　a　constant　absorbed　dose.　Different　systems　saturated　with　O-2　or　N-2　did　not　lead　to　an　effectively　increase　in　the　degradation　of　diethylstilbestrol.　The　solution　in　alkaline　condition　was　benefit　for　the　degradation　of　diethylstilbestrol.　Organic　acids　produced　by　the　degradation　of　diethylstilbestrol　were　identified　using　ion　chromatography,　such　as　acetic　acid,　formic　acid　and　oxalic　acid.　Diethylstilbestrol　radiolysis　may　be　caused　by　that　center　dot　OH　attacked　diethylstilbestrol　leading　to　the　open　of　benzene　ring　and　generation　of　organic　acids.