Seismic　wave　propagation　across　rock　masses　with　thin-layer　joints　by　the　modified　displacement　discontinuity　method　(M-DDM)　is　of　great　importance　for　geophysical　surveys.　The　M-DDM　introduces　a　frequency-dependent　effective　stiffness　to　describe　the　dynamic　stress-closure　relationship　of　a　thin-layer　joint.　We　verify　the　accuracy　of　M-DDM　in　studying　seismic　wave　propagation　across　rock　masses　with　thin-layer　joints.　Subsequently,　we　evaluate　the　influence　of　the　joint　thickness　and　the　incident　wave　frequency　on　M-DDM　accuracy.　We　analyze　the　prediction　error　of　the　transmission　coefficient　obtained　with　M-DDM.　The　results　demonstrate　that　the　frequency-dependent　effective　joint　stiffness　increases　with　increasing　incident　wave　frequency　and　decreases　with　increasing　joint　thickness.　Compared　with　the　traditional　displacement　discontinuity　method　(DDM),　M-DDM　more　accurately　predicts　the　transmission　coefficients　of　seismic　waves　propagating　across　thin-layer　joints.　The　transmission　coefficient　prediction　error　obtained　based　on　M-DDM　increases　with　increasing　joint　thickness　and　incident　wave　frequency　and　is　always　smaller　than　that　obtained　based　on　DDM.　Therefore,　the　M-DDM　can　be　used　to　effectively　investigate　seismic　wave　propagation　across　rock　masses　with　thin-layer　joints.　©　2024　Society　of　Exploration　Geophysicists.　All　rights　reserved.