Oil　impregnated　paper　is　an　important　solid　insulation　dielectric　in　power　transformers.　Thus　it　is　very　significant　to　understand　the　dielectric　properties　of　the　oil　impregnated　paper.　In　this　paper,　a　conductivity　measuring　system　was　built　to　explore　the　conduction　mechanism　of　oil　impregnated　paper.　This　measuring　system　is　able　to　measure　the　conduction　current　in　the　samples.　Based　on　the　system,　the　mathematical　relationship　between　conduction　current　and　field　strength　was　studied　firstly.　The　results　show　that　the　conduction　current　in　oil　impregnated　paper　is　mainly　caused　by　electrons　injected　from　the　electrodes.　The　Schottky　coefficient　beta(s)　was　calculated　both　in　theoretical　and　experimental　methods,　and　both　results　are　in　good　agreement.　The　reasons　for　deviation　between　two　results　are　analysed.　The　conduction　current　of　aged　oil　impregnated　papers　were　measured　as　a　function　of　different　electrical　fields.　The　results　show　that　with　the　increase　of　aging　time,　the　conductivity　of　oil　impregnated　paper　increases　and　the　permittivity　decreases.