Water　medium　has　been　widely　used　in　decoupled　charge　blasting　due　to　its　high　efficiency　of　energy　transfer.　In　this　study,　water-coupling　presplit　blasting　is　investigated　theoretically　and　numerically　from　the　essential　mechanism　of　the　effect　of　stress　wave　parameters　(peak　pressure　Pb,　loading　rate　Lrand　attenuation　coefficient　alpha)　on　presplitting.　According　to　the　propagation　and　superposition　theory　of　stress　waves,　the　inter-hole　tangential　stress　peak　distributions　and　hole　spacings　under　different　stress　wave　parameters　are　analytically　given.　Further,　considering　the　role　of　stress　wave　parameters,　water-coupling　presplit　blasting　under　different　in-situ　stresses　6s　and　delay　intervals　Delta　t　are　investigated　with　air-coupling　presplit　blasting　as　a　comparison.　Through　LS-DYNA,　numerical　simulations　of　presplit　blasting　are　carried　out　to　verify　the　reliability　of　theoretical　analysis　and　further　study　their　effects　on　the　presplitting.　Both　the　theoretical　and　numerical　results　show　that　the　blasting　load　with　higher　Pb　and　lower　Lr,　alpha,　6s　and　Delta　t　favors　presplitting.　Under　the　same　Pb,　the　stress　superposition　range,　minimum　stress　peak　and　hole　spacing　of　water-coupling　presplit　blasting　are　larger　than　those　of　air-coupling　presplit　blasting.　The　numerical　results　of　the　crack　pattern　also　show　that　lower　Lr　will　change　the　crack　pattern　from　the　crushing　zone　extension　dominated　by　compression-shear　damage　to　the　main　crack　propagation　dominated　by　tensile　damage,　and　the　directionality　of　presplitting　is　more　pronounced　with　higher　Pb　and　lower　Lr,　6sand　Delta　t.　Compared　with　air　medium,　water　medium　has　better　performance　in　the　directional　effect　of　presplitting　and　anti-interference　ability　to　the　delay　scatter　due　to　its　lower　Lr.