Thermal　steam　technology　for　coalbed　methane　extraction　is　an　intensive　research　focus.　This　paper　aims　to　explore　the　mechanism　of　thermal　steam　enhanced　coal　seam　permeability.　Computed　tomography,　Fourier　transform　infrared　spectroscopy,　and　high-pressure　methane　adsorption/desorption　were　selected　for　characterization　to　explore　the　effects　of　steam　at　100　and　200　°C　on　the　physicochemical　structure　and　methane　adsorption/desorption　properties　of　lignite　and　anthracite.　The　results　show　that　the　total　porosity　of　lignite　and　anthracite　increased　with　temperature　by　1.79%　and　1.38%　at　200　°C,　respectively.　Meanwhile,　the　3　D　fractal　dimension　and　absolute　permeability　of　lignite　and　anthracite　reach　maximum　values　of　2.25　and　2.19,　75.05　mD,　and　31.04　mD　at　200　°C,　respectively.　Moreover,　the　equivalent　diameter　distribution　of　pore　throats　shifts　toward　values　greater　than　300　μm　due　to　the　generation　of　well-connected　pores　and　fractures　after　thermal　steam　treatment.　It　can　reduce　the　hydroxyl　groups　and　the　sulfur　content　in　coal,　lower　the　average　chain　length,　decrease　coal　aliphaticity,　increase　aromaticity,　and　thus　lead　to　an　increase　in　coal　rank.　As　the　temperature　increases,　the　methane　adsorption　and　desorption　characteristic　parameters　a　and　1　n　values　of　lignite　and　anthracite　increase.　The　adsorption　characteristic　parameters　of　lignite　are　smaller　than　of　anthracite,　indicating　that　lignite　has　weaker　methane　adsorption　than　anthracite.　This　study　provides　a　theoretical　basis　for　the　application　of　thermal　steam　to　improve　the　extraction　efficiency　of　coalbed　methane.　©　2025　Author(s).