Unveiling　the　mechanical　and　failure　characteristics　of　flawed　granite　subjected　to　high-temperature　(HT)　cycles　is　essential　for　assessing　the　stability　of　underground　engineering.　There　is　limited　advanced　knowledge　of　the　rock　performance　under　HT　cycles　even　today.　To　that　end,　biaxial　compression　experiments　with　the　simultaneous　acoustic　emission　(AE)-digital　image　correlation　(DIC)　monitoring　are　conducted　on　flawed　granite　containing　the　flaw　pairs,　with　the　emphasis　on　the　influences　of　HT　cycles　on　the　mechanical　and　failure　characteristics　of　flawed　granite.　Experimental　results　suggest　that　the　rock　strength　is　increased　at　400　°C,　regardless　of　the　cycle　number,　while　it　is　weakened　at　600　°C,　especially　under　the　thermal　cycles.　By　the　coupling　analysis　of　acoustic-optical-mechanical　data,　the　levels　of　cracking　in　flawed　granite　are　revealed　as　the　process　zone　nucleation　and　quasi-static　growth,　along　with　the　macrocrack　initiation,　propagation,　and　coalescence　until　the　eventual　failure,　dictated　by　the　stress　shielding　effect　and　stress　amplification　effect.　The　splitting　crack,　hook　crack,　and　far-field　network　crack　are　reported　for　the　first　time.　Moreover,　the　flawed　granite　at　different　temperatures　transitions　from　tensile-dominated　cracks　to　mixed　tensile-shear　(T-S)　cracks.　Besides,　thermal　cycling　causes　rock　fatigue　damage,　and　the　alternating　thermal　stress　generated　by　HT　cycling　promotes　the　initiation　and　propagation　of　microcracks,　leading　to　the　development　and　further　intensification　of　thermally　induced　fracture.　©　2024　Elsevier　Ltd