NO.　and　O-.(2)-　combine　each　other　to　form　peroxynitrile　(ONOO-)　in　vivo.　Peroxyintrite　is　very　cytotoxic.　and　it　damages　many　biomolecules.　3-nitrotyrosine　and　dityrosine　are　two　main　products　from　the　reaction　of　ONOO-　and　tvrosine.　Lots　of　metallic　ions　in　vivo　influence　the　modification　of　tyrosine　by　perioxynitrite.　UV-Vis　and　Fluorescence　spectrophotometer　were　used　to　study　the　catalysis　and　inhibition　of　metallic　ions　on　the　production　of　3-nitrotyrosine　and　dityrosine　in　vitro.　Present　results　showed　that　Co(II),　Cu(II)　and　Mn(II)　enhance　the　production　of　3-nitrotyrosine.　and　among　them　Co(II)　and　Mn(II)　have　been　reported　rarely　hefore　about　it.　In　addition　inhibits　the　production　of　dityrosine　to　a　certain　extent.