DSA-type　Ti/Ir　x　Sn　1-x　O　2　electrodes　were　prepared　by　thermal　decomposition　method.　The　first-principles　calculations　were　employed　to　study　the　effects　of　the　doping　element　and　its　content　to　the　main　oxides　on　the　relationship　between　the　electronic　structures　and　the　photoelectrocatalytic(PEC)　activity　of　Ti/Ir　x　Sn　1-x　O　2　electrodes.　The　performance　of　the　coatings　was　characterized　using　XRD,　XPS,　LSV　and　EIS.　The　results　showed　that:　the　band　gap　decreased　with　the　increase　of　Ir　content.　An　impurity　level　appeared　in　the　forbidden　band,　which　was　conducive　to　the　separation　of　photogenerated　electrons　and　holes,　improving　the　conductivity　and　photocatalytic　activity　of　the　electrodes.　However,　the　excessive　content　of　Ir　would　promote　the　recombination　of　electrons　and　holes　and　reduce　the　band　gap.　When　the　Ir　content　was　above　25%,　the　forbidden　band　of　the　oxide　coating　could　disappeare.　The　conductivity　of　the　coating　further　improved,　it　sacrificed　the　photogenerated　carriers　and　thus　reduced　photocatalytic　activity　of　the　electrode.　Besides,　reducing　band　gap　would　weaken　the　redox　ability　of　photo　generated　electron-hole　pair.　Therefore,　The　PEC　activity　of　the　Ti/Ir　x　Sn　1-x　O　2　electrodes　was　mainly　depened　on　the　effects　of　Ir　content　on　the　electronic　structures　of　the　Ir　x　Sn　1-x　O　2　coatings.　In　our　experiments,　the　Ti/Ir　0.0625　Sn　0.9375　O　2　electrode　exhibited　better　PEC　properties.　©　2017　Elsevier　B.V.