An　Integrated　torque　model　for　a　swash-plate-type　water　hydraulic　axial　piston　motor　(WHAPM)　with　four　symmetrical　pre-compression　angles　has　been　developed　according　to　the　physicochemical　characteristic　differences　between　raw　water　and　mineral　oil.　It　consists　of　a　torque　sub-model　(including　the　friction　effect)　and　a　dynamic　pressure　sub-model.　The　model　takes　several　factors　into　account,　such　as　water　characteristics,　the　effects　of　the　dynamic　pressure　inside　the　piston　chamber,　the　piston　dynamics,　the　piston　friction,　the　water　compressibility,　and　the　pre-compression　angle　at　the　starting　and　ending　points　of　the　inlet　and　outlet.　Numerical　simulation　was　performed　to　examine　the　effects　of　(a)　pre-compression　angle,　(b)　relief-groove　obliquity,　(c)　rotor　speed,　(d)　piston-chamber　dead　volume,　(e)　friction　and　(f)　viscous　damping　coefficient　on　the　dynamic　pressure　and　the　output　torque　characteristics.　The　results　indicate　that　the　pre-compression　angle　and　the　relief-groove　obliquity　have　significant　effects　on　the　torque　characteristics.　Moreover,　the　developed　theoretical　formulas　of　the　torque　transition　and　the　mean　torque　and　displacement　have　been　presented.