According　to　our　previous　report　[G.　Yan,　X.　Wang,　X.　Fu,　D.　Li,　Catal.　Today　93-95　(2004)　851],　commercially　available　HZSM-5s　with　different　Si/Al　ratio　and　0.017-0.057　wt%　of　iron　impurity　have　shown　good　photocatalytic　activity　for　ethylene　oxidation.　Their　activity　increased　with　the　increase　of　iron　content.　In　this　paper,　photoactive　sites　in　these　commercial　HZSM-5　zeolites　were　studied　by　UV　Raman　spectroscopy.　The　results　showed　that　the　photocatalytic　activity　of　HZSM-5s　was　well　correlated　with　the　amount　of　two　types　of　isolated　iron　species.　The　iron　oxide　and　hydroxide　clusters　dispersed　on　the　zeolite　surface　were　not　photocatalytically　active.　The　possible　mechanism　of　the　photocatalysis　on　zeolites　was　also　discussed.