Steady-state　and　pulse　radiolysis　experiments　have　been　performed　to　gain　insight　into　the　mechanism　of　Thiamphenicol　(THA)　and　Florfenicol　(FLO)　degradation　in　aqueous　solutions.　Redox　reactions　of　aqueous　THA　and　PLO　solutions　with　center　dot　OH,　e(aq)(-),　and　center　dot　H　were　studied　by　using　pulse　radiolysis　techniques.　The　results　indicated　that　the　reaction　pathway　between　THA/FLO　and　center　dot　OH　was　dominated　by　the　initial　solution　pH　value.　In　neutral　condition,　the　addition　reaction　happened　between　center　dot　OH　and　benzene　ring.　The　rate　constants　for　the　reactions　of　center　dot　OH　with　THA　and　FLO　were　found　to　be　1.09　X　10(8)　L.mol(-1).　s(-1)　and　3.14　X　10(8)　L.mol(-1).s(-1)　respectively.　But　in　alkaline　condition,　the　organic　bond　OH-　was　removed　by　center　dot　OH.　The　dechlorination　of　THA　and　PLO　was　caused　by　e(aq)(-)　attacking.　The　center　dot　H　added　on　the　benzene　ring　forming　relative　stable　products,　and　the　rate　constants　for　the　reactions　of　center　dot　OH　with　THA　and　FLO　were　3.52　X　10(7)　L.mol(-1).s(-1)　and　2.43　X　10(8)　L.mol(-1).s(-1),　respectively.　The　reaction　in　alkaline　solution　was　also　discussed.　The　radiolysis　degradation　by-products　were　identified　by　GC/MS　analysis　and　their　degradation　pathway　were　also　conducted.