Z-scheme　van　der　Waals　(vdW)　heterostructure　photocatalysts　for　overall　water　splitting　have　drawn　significant　attention　due　to　their　strong　redox　ability　and　efficient　separation　of　photogenerated　electrons　and　holes.　Here,　by　using　first-principles　calculations,　we　predicted　that　the　transfer　of　photogenerated　electrons　and　holes　in　the　WTe2/InSe　vdW　heterostructure　follows　the　Z-scheme　pathway　instead　of　type-II.　It　is　highlighted　that　the　WTe2/InSe　vdW　heterostructure　is　an　indirect　bandgap　semiconductor　with　high　lattice　dynamical　and　thermodynamic　stability.　Interestingly,　the　built-in　electric　field　at　the　interface　can　effectively　separate　photogenerated　carriers.　The　suitable　band　edge　positions　of　the　WTe2/InSe　vdW　heterostructure　can　provide　sufficient　driving　force　for　photoinduced　carriers　to　participate　in　water　redox　reaction.　More　importantly,　the　Te-vacancies　in　WTe2/InSe　can　significantly　lower　the　overpotential　of　the　hydrogen　evolution　reaction　(HER).　Under　light　irradiation,　both　HER　and　oxygen　evolution　reaction　(OER)　can　spontaneously　occur　on　the　surface　of　the　WTe2/InSe　vdW　heterostructure　when　pH　＞　7.　These　results　provide　new　prospects　for　designing　efficient　InSe-based　Z-scheme　vdW　heterostructure　photocatalysts.