In　this　study,　we　investigate　Pd3-cluster-modified　555–777　graphene　(Pd3-graphene)　as　a　novel　resistor-type　gas　sensor　to　detect　SF6　decomposition　products　based　on　density　functional　theory　calculations.　We　obtained　and　minutely　analyzed　the　relevant　parameters　of　each　most　stable　adsorption　configuration　to　explore　the　microscopic　mechanism　during　gas　adsorption.　Theoretical　results　reveal　that　Pd3-graphene　shows　great　adsorption　capacity　and　sensitivity　toward　those　decompositions.　High　adsorption　energies　and　abundant　charge　transfer　amounts　could　guarantee　a　stable　adsorption　structure　of　decomposition　gases　on　Pd3-graphene　surface.　The　complex　change　of　density　of　states　verifies　a　strong　chemical　reaction　between　the　gases　and　the　surface.　Moreover,　the　conductivity　of　Pd3-graphene　would　improve　due　to　the　decrease　of　energy　gap,　and　the　sensitivity　was　calculated　as　SOF2　＞　H2S　＞　SO2　＞　SO2　F2.　This　work　provides　an　effective　method　to　evaluate　the　operation　status　of　SF6　gas-insulated　equipment.　©　2020　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.