Polybrominated　diphenyl　ethers　(PBDEs)　spread　widely　in　the　environment　are　mainly　removed　by　photochemical　and　anaerobic　microbial　degradation.　In　this　paper,　the　decomposition　of　4-bromodiphenyl　ether　(BDE　-3),　the　PBDEs　homologues,　is　investigated　by　electron　beam　irradiation　of　its　ethanol/water　solution　(reduction　system)　and　acetonitrile/water　solution　(oxidation　system).　The　radiolytic　products　were　determined　by　GC　coupled　with　electron　capture　detector,　and　the　reaction　rate　constant　of　e(sol)(-)　in　the　reduction　system　was　measured　at　2.7x10(10)　L.mol(-1).s(-1)　by　pulsed　radiolysis.　The　results　show　that　the　BDE-3　concentration　affects　strongly　the　decomposition　ratio　in　the　alkali　solution,　and　the　reduction　system　has　a　higher　BDE-3　decomposition　rate　than　the　oxidation　system.　This　indicates　that　the　BDE-3　was　reduced　by　effectively　capturing　e(sol)(-)　in　radiolytic　process.