Water　hydraulic　technology　has　been　developing　rapidly　over　the　past　decades　due　to　its　outstanding　advantages,　including　cleanliness,　security,　environmental　protection　and　cost-effectiveness　and　so　on.　At　present,　the　research　and　development　of　water　hydraulic　servo　valve　with　the　performance　of　high　precision,　frequency　response　and　high　reliability　become　an　important　direction　of　water　hydraulic　technology.　Hydrostatic　bearing　technology　has　been　used　at　the　both　ends　of　the　spool　in　order　to　reduce　the　leakage　losses　and　form　good　lubrication　characteristics　between　valve　spool　and　sleeve　in　the　water　hydraulic　servo　valve.　Based　on　hydrostatic　bearing　theory　the　mathematical　model　of　water　film　pressure　chamber　stiffness　and　bearing　capacity　is　established.　Through　the　analysis　of　throttling　by　clearance　between　spool　and　sleeve　and　annular　clearance　in　the　flapper-nozzle　system,　the　pressure-flow　characteristic　equation　of　flapper-nozzle　system　and　the　pressure　characteristic　equation　in　the　case　of　zero　flow　is　established,　and　then　the　equation　of　the　clearance　and　nozzle　between　the　spool　and　sleeve　is　deduced　after　some　simulation　analysis.　It　is　shown　that　the　application　of　hydrostatic　bearing　technology　can　form　static　pressure　lubrication　between　the　valve　spool　and　sleeve.　In　addition,　the　linear　relationship　of　the　pressure-flow　performance　of　the　flapper-nozzle　valve　is　maintained,　but　the　pressure　performance　of　which　become　worse.　Therefore,　it　necessary　to　select　the　linear　district　reasonably.