This　study　investigated　the　effects　of　cooling　thermal　shock　on　the　P-wave　velocity　of　granite　and　analyzed　its　microstructure.　First,　specimens　were　heated　to　high　temperatures　(400,　500,　600,　and　800　degrees　C),　and　then　subjected　to　cooling　thermal　shock　induced　by　immersion　in　water,　half　immersion　in　water,　and　near-water　cooling.　Subsequently,　ultrasonic　wave　tests　were　performed　to　study　the　effects　of　different　cooling　thermal　shocks　on　the　P-wave　velocity　and　damage　factor　calculated　by　the　P-wave　velocity.　The　gradient　distribution　characteristics　of　the　P-wave　velocity　with　increasing　distance　from　the　water　surface　were　investigated　after　near-water　cooling　thermal　shock.　Finally,　a　microcomputed　tomography　(CT)　test　was　further　performed　for　the　microstructural　explanation,　and　the　porosity　(the　percentage　of　the　volume　of　microcracks　to　the　total　volume　of　the　analyzed　region)　was　calculated　based　on　the　CT　image　processing　technique　to　quantify　the　microscopic　damage.　The　results　show　that　the　granite　after　immersion　in　water　cooling　thermal　shock　exhibits　the　lowest　P-wave　velocity　and　maximum　damage　factor　and　porosity,　followed　by　half　immersion　in　water　and　near-water　cooling.　The　generation　and　development　of　microcracks　induce　a　significant　decrease　in　the　P-wave　velocity.　The　variation　in　the　damage　factor　indicates　that　the　differences　in　the　influences　of　the　three　cooling　thermal　shocks　on　the　damage　of　granite　decrease　as　the　heating　temperature　increases.　For　the　near-water　cooling　thermal　shock,　the　P-wave　velocity,　damage　factor,　and　porosity　do　not　exhibit　evident　gradient　distributions.