A　novel　technology　to　determine　the　activity　of　xanthine　oxidase　(XOD)　through　the　chromogenic　reaction　of　4-aminoantipyrine(AAP),　phenic　acid(PA)　and　hydrogen　peroxide　(H2O2),　which　was　produced　via　the,　oxidation　of　xanthine　catalyzed　by　XOD,　under　the　help　of　horseradish　peroxidase　(HRP)　was　proposed.　The　influences　of　temperature,　pH　and　amount　of　substrate　on　the　activity　of　XOD　were　investigated.　The　optimal　conditions　to　determine　the　activity　of　XOD　were　obtained　as　follows:　horseradish　peroxidase　(7000　U/L),　4-aminoantipyrine　(1　mmol/L),　phenic　acid　(6　mmol/L)　and　xanthine　(1　mmol/L)　were　dissolved　in　50　mmol/L　Tris-HCl　buffer　solution　(pH　8.4),　the　reaction　temperature　was　3790,　the　reaction　time　was　20　min,　the　detective　wavelength　was　508　nm.　Under　the　conditions　mentioned　above,　the　linear　range　of　calibration　curve　was　between　5.0　U/L　and　100.0　U/L,　and　the　detection　limit　was　1.3　U/L.　All　these　show　this　technology　is　a　potential　alternative　method　to　determine　the　activity　of　XOD　in　the　areas　such　as　laboratory　and　clinical　diagnosis　etc.