Ablation　characteristics　is　a　key　factor　in　the　surface　flashover　of　insulation　materials　for　vacuum　insulators.　The　influence　of　nano/micro　Al2O3　and　Al(OH)3　fillers　on　the　ablative　resistance　of　epoxy　vacuum　insulation　material　has　been　investigated　by　repeated　flashovers　in　vacuum　under　microsecond　pulses.　It　was　found　that　the　ablative　resistance　of　Al(OH)3　filler　is　much　better　than　that　of　Al2O3　and　that　the　nano-filler　is　more　effective　than　the　micro-filler　in　the　case　of　Al(OH)3,　whereas　in　Al2O3　the　opposite　applies.　A　thermal-electrical　coupled　3-dimensional　finite　element　simulation　model　has　been　developed　to　describe　the　results　and　analyze　them　in　terms　of　the　thermal　characteristics　of　the　particles.　The　model　shows　that　although　both　Al2O3　and　Al(OH)3　fillers　can　improve　the　ablative　resistance　of　the　epoxy　composites,　with　Al(OH)3　being　the　better　material.　The　mechanism　whereby　this　occurs　is　different　in　the　two　cases,　with　the　dehydration　reaction　dominating　for　Al(OH)3　and　the　mass　degradation　dominating　for　Al2O3.