Water　hydraulic　servo　valve　has　become　an　important　research　subject　nowadays,　and　its　secondary　amplifier　usually　uses　slide　valve.　Research　on　flow　characteristics　of　water　hydraulic　slide　valve　is　important　to　the　design　of　water　hydraulic　servo　valve.　Based　on　the　classical　theory　of　incompressible　flow,　CFD　software　FLUENT　is　used　to　simulate　and　analyze　the　flow　characteristics　of　water　hydraulic　slide　valve.　Simulations　with　different　boundary　values　are　applied　to　the　same　slide　valve　in　order　to　guarantee　the　accuracy　of　the　simulation　results.　Detailed　comparisons　are　made　between　throttles　with　different　structure　parameters,　including　spool　diameter,　spool　opening,　flow　passage　diameter　and　equalizing　slots　so　as　to　define　the　parameters　respectively.　The　results　indicate　that　the　flow　rate　of　the　slide　valve　designed　is　approximately　proportional　to　the　spool　opening　within　certain　travel.　Finally,　the　structure　parameters　of　the　slide　valve　that　satisfy　the　design　requirements　are　obtained.　The　simulation　results　provide　theoretical　basis　for　the　design　and　improvement　of　water　hydraulic　slide　valve　used　in　water　hydraulic　servo　valve.　©　(2010)　Trans　Tech　Publications,　Switzerland.