The　effect　of　barrier　material　on　AC　breakdown　voltages　of　a　hybrid　gas-solid　insulation　is　investigated　by　examining　the　behavior　of　electrostatic　potential　on　barrier　surfaces.　Breakdown　characteristics　of　air-insulated　gaps　with　barriers　made　of　three　different　polymeric　materials　are　experimentally　investigated.　Further,　measurements　of　surface　potential　on　the　barriers　are　performed　and　the　results　are　utilized　to　obtain　surface　charge　dynamic　characteristics　for　the　three　polymeric　materials　and　extract　their　electric　conductivities,　charge　carrier　mobilities,　and　trap　energy　distributions.　It　is　found　that　the　material　with　the　lowest　initial　surface　potential　and　fastest　decay　rate　exhibits　the　highest　bulk　conductivity　and　carriers＇　mobility,　as　well　as　the　lowest　trap　energy　level.　These　properties　provide　the　highest　increase　in　AC　breakdown　voltages　compared　with　pure　air.　It　is　concluded　that　materials　where　the　accumulation　of　charges　in　the　bulk　is　inhibited　and　decay　of　surface　charges　is　facilitated,　allow　for　higher　operating　voltages　of　AC　hybrid　gas-solid　insulation　systems.　The　mechanism　of　the　effect　of　barrier　material　on　AC　breakdown　voltage　is　discussed.　©　IEEE.　2015　CSEE.