Pore-water　pressure　(PWP)　induced　by　root　water　uptake　has　usually　been　investigated　by　individual　physical　quantities.　Limited　dimensional　analysis　has　been　available　for　investigating　PWP　response　in　a　vegetated　slope.　In　this　study,　dimensional　analysis　was　conducted　to　explore　dimensionless　numbers　controlling　PWP　distributions　in　a　vegetated　slope.　Three　dimensionless　numbers　governing　unsaturated　seepage　were　proposed,　including　capillary　effect　number　(CN,　describing　the　relative　importance　of　water　flow　driven　by　PWP　gradient　over　that　driven　by　gravity),　root　water　uptake　number　(RN,　representing　the　effects　of　root　water　uptake),　and　water　transfer-storage　ratio　(WR,　ratio　of　water　transfer　to　water　storage　rate).　Dimensionless　relationships　were　further　proposed　to　estimate　PWP　and　root　influence　zone　in　a　vegetated　slope.　Then　analytical　parametric　studies　were　conducted　to　study　effects　of　RN,　CN,　and　WR　on　PWP　distributions.　Thereafter,　the　proposed　relationships　were　validated　by　published　field　and　centrifuge　tests.　During　the　drying　period,　the　effects　of　root　water　uptake　on　PWP　and　the　root　influence　zone　become　more　significant　as　CN　decreases　or　RN　increases.　During　the　wetting　period,　the　larger　the　WR,　the　deeper　the　wetting　front　moves　and　more　reduction　of　negative　PWP　occurs.　The　proposed　dimensionless　relationships　can　determine　PWP　and　the　root　influence　zone　in　a　vegetated　soil　reasonably　well.