Moisture　has　a　great　effect　on　the　microstructure　of　mudstone　and　the　stability　of　muddy　strata.　Due　to　many　clay　minerals　in　mudstone,　swelling　deformation　and　even　disintegration　occur　during　moisture　diffusion,　accom-panied　by　energy　storage　and　release.　To　reveal　the　deterioration　mechanism　and　energy　characteristics　of　mudstone　induced　by　moisture　diffusion,　firstly,　the　Weibull　distribution　function　is　introduced　into　the　FDEM-based　moisture　diffusion-fracture　coupling　model　to　consider　the　heterogeneity　of　swelling　deformation　and　stress　of　mudstone　minerals.　Then,　the　microfracture　behavior　and　energy　evolution　of　heterogeneous　mudstone　during　moisture　diffusion　are　studied　using　the　coupling　model.　Results　indicate　that　the　nonuniform　swelling　deformation　between　particles　is　the　main　reason　for　the　microfracture,　both　tensile　and　shear　failures　occur　in　mudstone.　The　evolution　of　kinetic　energy　can　be　divided　into　three　stages,　while　that　of　strain　energy　depends　on　the　storage　rate　by　swelling　deformation　and　the　release　rate　by　microfracture　in　mudstone　during　moisture　diffusion.　When　the　storage　rate　is　greater　than　the　release　rate,　the　evolution　of　strain　energy　is　divided　into　two　stages.　Otherwise,　it　is　divided　into　three　stages.　Besides,　the　effects　of　homogeneity　index,　swelling　coefficient,　and　moisture　content　on　the　microcrack　morphology　and　energy　evolution　are　also　discussed.　Finally,　the　microcrack　morphology　and　energy　evolution　of　mudstone　under　different　moisture　loading　conditions　are　investigated,　where　the　microcrack　morphology　under　the　surrounding　moisture　condition　agrees　well　with　the　experimental　results.　The　results　in　this　paper　provide　theoretical　value　for　studying　the　swelling　and　micro　-fracture　mechanism　of　mudstone　during　moisture　diffusion.