Granite　is　a　viable　host　for　deep　nuclear　waste　disposal　because　its　low　permeability　and　high　strength　enable　the　stable　and　safe　operation　of　the　repository.　We　examined　the　evolution　of　the　permeability　and　triaxial　mechanical　behaviour　of　granite　after　high-temperature　treatment.　First,　the　effect　of　the　high　temperature　on　the　physical　behaviour　and　permeability　evolution　of　granite　was　analysed　in　detail.　The　mass,　P-wave　velocity,　and　thermal　conductivity　of　granite　decrease,　but　the　volume　increases　with　increasing　temperature.　The　permeability　of　intact　granite　increases　by　four　orders　of　magnitude　as　the　cycled　temperature　increases　from　25　to　800　degrees　C.　Subsequently,　the　effect　of　high　temperature　on　the　triaxial　deformation　and　acoustic　emission　(AE)　behaviour　of　granite　was　investigated.　Under　uniaxial　compression　at　T　＜=　300　degrees　C,　the　stress　decreases　before　the　peak　strength　is　reached,　corresponding　to　a　significant　AE　event,　which　is　due　to　the　development　of　multiple　splitting　tensile　fractures　along　the　loading　direction.　At　T　＞=　450　degrees　C,　AE　event　is　observed　once　a　minor　stress　is　applied,　which　results　from　failure　is　controlled　by　thermally　induced　cracks.　However,　under　triaxial　compression,　the　temperature　has　little　effect　on　the　AE　characteristics.　The　granite　fails　along　the　shear　fracture　plane,　which　becomes　wider　with　increasing　confining　pressure.　At　T　＞=　600　degrees　C,　it　is　easier　to　form　intragranular　cracks　and　the　stress　quickly　decreases　after　the　peak　strength　is　reached.　The　shear　plane　is　smoother　under　high　confining　pressure.　Third,　the　effect　of　high　temperature　on　the　peak　strength　and　crack　damage　threshold　of　granite　was　further　analysed.　Generally,　under　uniaxial　compression,　the　peak　strength　and　crack　damage　threshold　first　remain　relatively　constant　at　T　＜=　300　degrees　C,　begin　to　decrease　at　T　=　450　degrees　C,　and　decrease　more　rapidly　at　T　=　600　degrees　C.　The　confining　pressure　notably　reduces　the　effect　of　the　temperature　on　the　peak　strength　and　crack　damage　threshold.　Finally,　the　effect　and　mechanism　of　high　temperature　on　the　triaxial　strength　parameters　of　granite　were　further　discussed.　At　T　＜=　300　degrees　C,　thermally　induced　cracks　are　not　notable　and　the　temperature　has　little　effect　on　the　strength.　At　450　degrees　C　＜=　T　＜=　600　degrees　C,　thermally　induced　cracks　are　more　notable　and　the　temperature　has　a　significant　effect　on　the　strength　behaviour.　Because　of　the　thermal　stress　released　by　thermal　macrocrack　formation,　the　continuous　increase　in　the　temperature　has　little　impact　on　strength.