The　construction　of　an　elastoplastic　constitutive　model　for　energy　dissipation　and　crack　evolution　in　rocks　is　crucial　for　accurately　predicting　their　failure　processes.　This　study　first　constructs　a　theoretical　elastoplastic　constitutive　model　by　analyzing　the　mechanical　properties　of　rocks,　energy　dissipation,　and　crack　evolution　under　conventional　triaxial　compression.　Subsequently,　a　three-dimensional　finite　difference　scheme　for　the　theoretical　model　is　derived　to　implement　a　numerical　algorithm.　Finally,　using　argillaceous　siltstone　as　an　example,　the　validity　of　the　theoretical　model　and　its　algorithmic　implementation　is　verified　through　experimental　testing,　result　analysis,　model　construction,　secondary　development,　and　numerical　simulation.　The　research　indicates　that　the　dissipated　energy　is　equal　to　the　integral　of　the　stress–strain　curve　minus　the　elastic　strain　energy,　which　can　be　quantitatively　described　using　strength　parameters.　The　volumetric　strain　of　cracks　is　equal　to　the　plastic　volumetric　strain,　which　can　be　indirectly　quantified　using　the　dilation　angle.　The　simulated　stress–strain　curves　closely　align　with　the　experimental　data,　and　the　simulated　dissipated　energy　and　crack　volumetric　strain　are　consistent　with　the　theoretical　calculations,　confirming　that　the　theoretical　model　effectively　captures　the　nonlinear　mechanical　behavior,　energy　dissipation,　and　crack　evolution　of　rocks.　©　2025　by　the　authors.