To　improve　the　efficiency　of　coalbed　methane　and　recoverability　of　reservoirs,　enhanced　fracturing　technology　is　usually　required　to　improve　the　low　porosity　and　permeability　status　of　coal　reservoirs.　As　a　feasible　method　for　strengthening　permeability,　microwave–LN2　freeze–thaw　(MLFT)　cycles　modify　the　microscopic　pore　structure　of　coal　through　the　coupled　effect　of　temperature　stress　changes,　phase　change　expansion,　and　fatigue　damage.　1H　nuclear　magnetic　resonance　combined　with　fractal　dimension　theory　was　used　to　characterize　quantitatively　the　pore　system　and　geometric　features　of　coal.　The　geometric　fractal　model　constructed　using　the　T2　spectrum　indicates　that　the　fractal　dimensions　Dp　and　De　have　high　fitting　accuracy,　demonstrating　that　percolation　and　effective　pores　exhibit　good　fractal　characteristics.　Dp　and　De　are　correlated　negatively　and　positively,　respectively,　with　the　cyclic　parameters.　The　relevance　analysis　shows　that　the　NMR　fractal　method　can　reflect　the　pore–fracture　heterogeneity　of　coal,　which　has　a　significant　effect　on　the　percentage　of　fluid　migration　space.　This　study　reveals　that　MLFT　cycles　have　significant　enhancement　effects　on　promoting　the　extension　of　multi-type　pores　structures　within　the　coal　matrix,　as　well　as　the　connectivity　and　permeability　of　cracks.　©　International　Association　for　Mathematical　Geosciences　2024.