Simulation　investigation　on　fluid　characteristics　of　the　water　hydraulic　jet　pipe　servo　valve　(WHJPSV)　is　conducted　through　a　commercial　computational　fluid　dynamics　(CFD)　software　package　FLUENT.　In　particular,　the　factors　to　fluid　characteristics　of　WHJPSV　are　addressed,　which　include　diameter　combination　of　jet　pipe　and　receiver　pipe,　jet　pipe　nozzle　clearance,　angle　between　two　jet　receiver　pipes　and　deflection　angle　of　the　jet　pipe.　It　is　concluded　from　the　results　that:　(i)　Structural　parameters　have　great　influences　on　fluid　characteristics　of　WHJPSV,　when　d　1　=　d　2　=　0.3　mm,　α=　45°,　b　=　0.5　mm,　and　the　simulation　exhibits　better　fluid　characteristics;　(ii)　The　magnitude　of　the　recovery　pressure　and　flow　velocity　increase　almost　linearly　with　the　deflection　angle　of　jet　pipe.　The　research　work　in　this　paper　is　important　for　determining　and　optimizing　the　structural　parameters　of　the　jet　pipe　and　jet　receiver.　The　relevant　conclusions　could　be　extended　to　the　study　of　other　water　hydraulic　servo　control　components.　©　2011　Shanghai　University　and　Springer-Verlag　Berlin　Heidelberg.