High　velocity　debris　is　a　major　threat　to　the　safety　of　the　surrounding　area　during　an　explosion　accident.　Since　reinforced　concrete　(RC)　is　the　most　universal　civil　and　military　building　material,　it　is　of　great　significance　to　study　the　characteristics　and　launching　trajectory　of　debris　following　a　blast　load.　In　this　study,　based　on　the　LS-DYNA　software,　the　dynamic　failure　process　of　an　RC　slab　under　an　internal　blast　load　is　first　investigated　using　the　Arbitrary　Lagrangian-Eulerian　(ALE)　method　and　the　multi-material　fluid-solid　coupling　method.　For　fulfilment,　a　zero-thickness　cohesive　element　is　introduced　to　simulate　the　concrete　failure　under　a　blast　load　in　order　to　avoid　the　mass　loss　caused　by　a　conventional　element　erosion　algorithm.　Then,　since　it　is　very　time-consuming　to　conduct　an　LS-DYNA　simulation　through　to　the　end,　which　is　when　all　the　debris　has　landed　on　the　ground,　a　faster　scheme　is　proposed　in　tandem　with　the　LS-DYNA　numerical　analysis　to　predict　the　flight　path　and　scattering　pattern　of　the　debris　produced.　Finally,　the　size　distribution,　launching　angle,　launching　velocity　and　projectile　distance　of　the　debris　following　the　breakup　of　the　RC　slab　under　different　internal　blast　loads　are　analysed.