For　micro-small　high-speed　on-off　valves,　large　flow　and　high-frequency　response　increase　the　flow　force　of　the　spool　and　affect　its　motion　state.　Therefore,　analysis　and　compensation　of　the　flow　force　are　the　key　factors　to　improve　the　performance　of　the　valve.　To　solve　the　problem　that　the　traditional　steady-state　flow　force　theory　calculation　formula　is　not　applicable　due　to　the　complex　flow　field　structure　of　the　ball　valve　high-speed　on-off　valve　in　high-frequency　opening　and　closing　state,　the　CFD　method　was　used　to　study　the　flow　force.　Firstly,　COMSOL　software　was　utilized　to　establish　the　geometric　model　of　the　fluid　field.　Then,　the　pressure　and　streamline　distribution　diagram,　flow　curves,　and　steady-state　flow　force　curves　of　the　valve　ball　and　spool　under　different　valve　openings　were　obtained　by　using　the　weakly　compressible　fluid　and　standard　k–ε　turbulence　model　and　dynamic　grid　technology.　Finally,　to　compensate　for　the　reduced　steady-state　flow　force,　the　valve　port　structure　was　optimized　and　the　optimal　parameters　were　determined　according　to　the　relationship　between　different　valve　port　structure　parameters　and　the　force　of　the　valve　core,　and　the　opening　and　closing　time　of　the　valve　port.　The　results　showed　that　the　steady-state　flow　force　of　the　valve　ball　in　the　oil　inlet　hole　would　decrease　first　and　then　increase　with　the　opening　of　the　valve　port,　but　the　steady-state　flow　force　of　the　valve　ball　in　the　oil　inlet　hole　was　smaller　than　that　of　the　valve　ball　in　the　oil　return　hole,　so　the　steady-state　flow　force　change　on　the　spool　was　similar　to　that　on　the　valve　ball　in　the　oil　return　hole.　Reducing　the　diameter　of　the　push　rod　and　changing　the　flow　channel　into　a　gradually　expanding　flow　channel　could　effectively　compensate　for　the　reduced　steady-state　flow　force.　Compared　with　the　original　structure,　the　opening　and　closing　time　of　the　improved　optimal　structure　decreased　from　1.047　ms　to　0.714　ms,　and　the　steady-state　flow　force　compensation　effect　was　obvious.　©　2023　Editorial　Department　of　Journal　of　Sichuan　University.　All　rights　reserved.