Fe3O4/FeS2　catalyst　was　successfully　prepared　by　hydrothermal　method,　and　employed　to　mediate　a　heterogeneous　Fenton　system　for　the　remediation　of　a　typical　phenylarsonic　acid　pollutant　(roxarsone,　ROX).　The　characterization　results　of　XRD,　SEM,　XPS　and　magnetic　measurement　system　(VSM)　showed　that　Fe3O4/FeS2　displayed　evident　granular　particles　and　good　magnetic　properties.　The　results　of　ROX　degradation　experiments　showed　that　under　optimal　conditions　(4.5of　the　initial　pH,　20mg/L　of　ROX　initial　concentration,　0.15g/L　of　Fe3O4/FeS2　dosage　and　0.034g/L　of　H2O2　concentration),　the　heterogeneous　Fenton　system　could　instantaneously　degrade　96.74%　of　ROX　in　1min,　which　was　much　better　than　of　the　systems　mediated　by　sole　Fe3O4　or　FeS2.　In　addition,　Fe3O4/FeS2　could　be　effectively　recycled　by　magnets,　and　also　exhibited　good　reusability.　After　3　runs,　the　degradation　efficiency　of　ROX　was　still　over　80%.　Mechanism　analysis　revealed　that　plenty　of　hydroxyl　radicals　(OH)　could　be　generated　via　the　catalytic　reaction　between　Fe3O4/FeS2　and　H2O2.　Subsequently,　the　OH　could　quickly　attacked　the　C-As,　C-N,　and　C-C　bonds　in　the　ROX　molecule,　resulting　in　the　dearsenication,　denitrification　and　ring　opening　reactions,　as　well　as　the　formation　of　a　series　of　organic　products　(such　as　phenols,　quinones,　small　molecular　organic　acids,　etc.)　and　inorganic　products　(As(V)　and　NO3-).　Finally,　the　released　inorganic　arsenic　could　be　adsorbed　on　the　surface　of　the　catalyst,　while　the　organic　product　was　further　mineralized.　©　2021,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.