Solid　insulation　technology　in　medium　voltage　12kV　switchgear　has　been　widely　used.　In　order　to　realize　further　miniaturization,　weatherability,　security,　metallization　treatment　on　insulation　surface　has　become　a　new　research　in　solid　insulated　switchgear(SIS).　But　the　present　SISs　are　mostly　without　metallization　on　the　outer　epoxy　pouring　mold　surface,　the　purpose　of　this　paper　is　to　analyse　and　simulate　the　electric　field　distribution　characteristics　of　the　epoxy　casting　mold　in　a　12kV　SIS　when　without　metallization　on　epoxy　surface.　The　results　show　that　the　present　SISs　with　epoxy　mold　surface　nonmetallization　can　satisfy　the　electric　field　assessment,　but　the　internal　vacuum　interrupter　structure　and　the　distance　between　epoxy　mold　and　cabinet　shell　are　dominant.