In　situ　FTIR　spectroscopy　was　utilized　to　investigate　the　magnetic　field　effect　on　the　heterogeneous　photocatalytic　degradation　of　benzene　over　platinized　titania　(Pt/TiO2).　The　results　revealed　that　the　employment　of　magnetic　field　may　not　change　the　mechanism　of　photocatalytic　degradation　of　benzene,　however,　it　greatly　facilitate　the　conversion　of　benzene　to　phenol　and　quinone,　as　well　as　the　transformation　from　phenol　to　quinone,　resulting　in　opening　the　benzene　ring　easily　and　promoting　the　production　of　CO2.