The　vertical　van　der　Waals　heterostructures　based　on　2-D　materials　have　attracted　tremendous　attention　in　optoelectronic　devices　as　they　can　offer　perfect　interface　without　dangling　bonds,　atomic　layer　thicknesses,　and　conveniently　tunable　energy　band　alignment.　However,　the　carrier　transport　mechanism　in　vertically　stacked　van　der　Waals　heterostructure　photodetectors　is　usually　neglected　in　regards　of　photoresponse　enhancement　strategy,　leading　to　low　photoresponsivity　and　quantum　efficiency.　Here,　we　report　a　vertically　stacked　tunneling　photodetector　based　on　WSe2/graphene/WS2　van　der　Waals　heterostructure.　By　introducing　graphene　film　into　the　WSe2/WS2　interface,　the　interface　composition　was　ameliorated　and　the　Fowler-Nordheim　tunneling　(FNT)　was　enhanced　with　the　reduced　tunneling　barrier　height　and　thickness,　caused　by　the　elevated　energy　level　of　electrons　since　strong　electron-electron　interaction,　ultrafast　thermalization　(similar　to　50　fs),　and　massless　Dirac　electrons　of　graphene.　Therefore,　the　device　exhibits　a　high　photocurrent/dark　current　ratio　(＞10(4)),　fast　response　time　(similar　to　300　mu　s),　high　detectivity　(similar　to　1.58　x　10(12)　Jones),　and　high　responsivity　(429　mA　W-1)　across　a　broad　spectral　range　till　1　mu　m　at　room　temperature.　The　optimized　detectivity　and　responsivity　are　about　150　times　and　50　times　higher　than　WSe2/WS2　device　without　graphene,　respectively.　These　results　contribute　to　offer　a　novel　and　versatile　strategy　for　overcoming　the　performance　limitation　in　van　der　Waals　photodetector.