In　this　study,　a　simulation　model　of　surface　charge　accumulation　on　a　basin-type　insulator　was　constructed.　Three　accumulation　mechanisms　were　considered,　i.e.　electrical　conduction　within　the　gas,　electrical　conduction　through　the　insulator　and　along　insulator　surface.　For　the　gas　electrical　conduction,　the　generation,　diffusion,　drift　and　recombination　of　charge　carriers　in　SF6　were　taken　into　consideration.　The　surface　conductivity　is　treated　by　directly　defining　parameters　instead　of　surface　thin　layer,　which　improves　the　calculation　range　of　surface　conductivity　in　ion　flow　model.　Additionally,　surface　charge　accumulation　characteristics　with　different　parameters　were　studied.　The　results　indicated　that　the　polarity　of　surface　charge　would　change　with　the　ion　pair　generation　rate,　volume　conductivity　and　surface　conductivity.　Based　on　the　surface　charge　and　electric　field　distributions,　it　was　found　that　the　dominant　surface　charge　accumulation　mechanism　changes　from　volume　conduction　to　gas　conduction　as　the　ion　pair　generation　rate　increases.　When　the　volume　conductivity　increases　from　1?×?10-19　to　1?×?10-14　S/m,　the　dominant　mechanism　changes　from　gas　conduction　to　volume　conduction.　Furthermore,　as　the　surface　conductivity　increases,　the　dominant　mechanism　is　surface　conduction.　The　proposed　study　is　helpful　for　understanding　the　mechanism　of　surface　charge　accumulation　and　provides　insight　into　charge　accumulation　inhibition.　©　2019　The　Institution　of　Engineering　and　Technology.