In　the　process　of　geothermal　well　drilling,　the　high-temperature　rock　in　the　reservoirs　is　cooled　by　different　cooling　media,　which　leads　to　the　change　of　mechanical　properties,　affecting　the　rockbreaking　efficiency　of　the　bit.　Sandstone　and　granite　were　taken　as　the　research　objects　and　heated　to　400　degrees　C,　600　degrees　C,　and　800　degrees　C,　then　were　cooled　by　natural,　water,　and　liquid　nitrogen　(LN2)　cooling.　Ultrasonic　detector　tests,　the　split　Hopkinson　pressure　bar　(SHPB)　experiments,　and　scanning　electron　microscope　(SEM)　tests　were　conducted.　The　effects　of　heating　temperature　and　cooling　methods　on　the　dynamic　mechanical　properties　were　quantified　and　analyzed.　Thermal　shock　damage　evolution　and　the　damage　mechanism　of　high-temperature　rock　under　different　cooling　ways　were　discussed.　The　fractal　method　was　applied　to　the　analysis　of　fragment　distribution,　to　obtain　the　corresponding　relationship　between　fractal　dimension　and　heat　treatment　temperature　and　cooling　methods.　The　research　results　showed　that　thermal　and　cooling　treatment　has　a　significant　effect　on　the　mechanical　properties　of　rock.　With　the　increase　of　the　treatment　temperature,　the　dynamic　peak　stress　decreased,　and　the　peak　strain　increased.　The　temperature　sensitivity　of　sandstone　to　temperature　was　higher　than　that　of　granite,　while　sandstone　was　more　significantly　affected　than　granite　in　terms　of　the　sensitivity　of　the　cooling　method.　Fractal　dimension　could　be　used　to　analyze　the　fragmentation　of　high-temperature　rock　cooled　in　different　ways　after　impact.　The　experimental　results　were　expected　to　provide　an　adequate　theoretical　basis　for　the　development　and　utilization　of　geothermal　resources.　(c)　2022　The　Author(s).　Published　by　Elsevier　Ltd.