A　systematic　understanding　of　the　Pore　development　of　high-temperature　rocks　after　different　cooling　methods　can　provide　a　theoretical　basis　for　underground　coal　gasification,　geothermal　resource　exploitation　and　other　engineering.　In　this　study,　thermal-cooling　sandstones　with　three　different　cooling　methods　(natural　cooling,　liquid　nitrogen　cooling,　and　water　cooling)　were　tested　using　nuclear　magnetic　resonance　equipment,　and　the　generation　and　development　of　pores　and　fissures　in　thermal-treated　sandstones　were　observed.　Magnetic　resonance　imaging　was　used　to　analyze　the　spatial　distribution　and　connectivity　of　pores　in　the　thermal-treated　sandstones.　Scanning　electron　microscopy　was　used　to　analyze　the　thermal　damage　mechanism　of　the　thermal-cooling　sandstone.　The　results　show　that　the　porosity　of　sandstone　increased　gradually　with　the　increase　of　thermal　treatment　temperature,　and　the　maximum　increase　of　three　cooling　methods　reached　11.52　%,　13.82　%　and　17.05　%,　and　the　micropores　accounted　for　the　main　contribution　to　the　pore　development　of　thermal-cooling　treated　sandstone.　The　relationship　between　sandstone　damage　and　thermal　treatment　temperature　was　quantitatively　analyzed,　and　the　growth　rate　of　damage　coefficients　was　first　slow　and　then　fast,　with　500　°C　as　the　change　node.　Water　cooling　damage　value　is　the　largest,　liquid　nitrogen　cooling　damage　value　is　the　second,　and　natural　cooling　damage　value　is　the　smallest.　With　the　gradual　increase　of　thermal　treatment　temperature,　the　red　area　of　sandstone　magnetic　resonance　imaging　gradually　increases　and　forms　a　connected　area,　indicating　that　the　pores　of　the　specimens　rapidly　expand　and　penetrate　each　other　to　form　cracks.　The　pore　development　is　mainly　concentrated　in　the　outside　of　the　specimens　due　to　the　cooling　rate.　The　thermal　damage　mechanism　of　thermal-cooling　sandstone　was　analyzed.　When　the　sandstone　is　heated,　the　mineral　particles　undergo　physical　changes　(heating　expansion　and　water　evaporation)　and　chemical　changes　(mineral　phase　change　and　ion　dissociation),　resulting　in　intergranular　and　transgranular　cracks　inside　the　rock,　respectively.　On　cooling,　the　mineral　grains　contract　under　the　influence　of　thermal　stresses,　resulting　in　tensile　stress　within　the　rock.　Meanwhile,　hydrolysis　of　carbonate　mineral　and　expansion　of　clay　minerals　during　water　cooling　further　lead　to　the　development　of　intergranular　and　transgranular　cracks.The　superposition　effect　of　the　two　processes　of　high　temperature　and　cooling　creates　huge　thermal　stresses　inside　the　rock,　leading　to　further　development　of　pores　and　cracks,　and　becoming　the　main　reason　for　the　development　of　thermal　damage　in　sandstone.　©　2024　Elsevier　Ltd