Aiming　to　accurately　simulate　seismic　dynamic　response　of　rock　masses　using　the　numerical　manifold　method　(NMM),　boundary　settings　must　be　treated　carefully.　In　this　paper,　4　issues　in　boundary　settings　are　investigated　to　improve　the　performance　of　NMM:　(1)　Nonreflecting　boundaries　including　the　viscous　boundary　and　viscoelastic　boundary　are　considered;　(2)　A　free-field　boundary　is　incorporated　into　NMM　to　accurately　simulate　external　source　wave　motion;　(3)　A　seismic　input　boundary　is　considered,　and　the　force　input　method　is　introduced;　and　(4)　A　static-dynamic　unified　boundary　is　incorporated　for　the　convenience　of　transforming　displacement　boundary　into　other　types　of　boundaries,　such　as　nonreflecting　boundaries　and　seismic　input　boundary.　Several　benchmark　problems　are　solved　to　validate　the　improved　NMM.　Simulation　results　agree　well　with　analytical　ones,　indicating　that　the　improved　NMM　is　able　to　simulate　seismic　dynamic　response　of　rock　masses　reliably　and　correctly.