The　antibiotic　sulfamethazine　(SMT)　has　emerged　as　a　water　pollutant　that　is　recalcitrant　to　conventional　water　treatment　process.　A　number　of　technologies　based　on　hydroxyl　radical　or　sulfate　radical　induced　SMT　degradation　have　been　described,　but　photo-induced　degradation　is　not　widely　examined.　Herein,　photocatalysts　of　Bi-doped　TiO2　nano-composites　supported　by　powdered　activated　carbon　(PAC)　were　prepared,　with　variable　molar　ratios　of　Bi/Ti　(0.06:1(6%),　0.08:1(8%),　0.1:1(10%)　and　0.12:1(120/0))　by　a　sol-hydrothermal　method.　The　ratio　of　10%　(Bi-Ti/PAC　(10%))　was　most　efficient　to　degrade　SMT.　Experimental　variables　during　photocatalytic　degradation　were　optimized　for　solution　pH,　catalyst　dosage,　initial　SMT　concentration,　and　coexisted　anions.　Under　optimal　conditions　of　1.0　g/L　catalyst,　20　mg/L　initial　SMT　concentration,　pH　6.0　and　visible　light　irradiation　at　400-780　nm,　the　degradation　rate　reached　81.18%　in　300　min.　Compared　to　Bi-Ti(10%)　nano-composite　without　PAC,　pure　TiO2　or　commercially　available　P-25,　Bi-Ti/PAC(10%)　was　superior　for　SMT　degradation　with　a　degradation　kinetic　rate　of　0.00531　min(-1).　The　properties　of　the　prepared　photocatalysts　were　characterized　by　X-ray　powder　diffraction,　scanning　electron　microscope,　X-ray　photo-electron　spectroscopy,　Brunauer-Emmett-Teller　and　ultraviolet-visible　diffuse　reflection　spectroscopy.　This　revealed　that　Bi-Ti/PAC　(10%)　had　a　smaller　crystal　size,　larger　specific　surface　area,　larger　pore　size,　stronger　visible　light　absorption　ability　and　lower　band　gap　energy　than　pure　TiO2.　Ten　intermediates　of　SMT　were　identified　and　a　possible　degradation　pathway　was　proposed.