Using　particle　image　velocimetry　(PIV)　experiments　and　CFD　numerical　simulation,　the　flow　characteristics　of　the　oil　cavity　in　the　hydrostatic　support　system　of　high-end　CNC　machine　tools　have　been　investigated.　The　influences　of　inlet　Reynolds　number　(Re),　oil　cavity　depth　(H)　and　clearance　height　(h)　on　vortex　structures,　wall　pressure　and　shear　stress　distribution　in　the　oil　cavity　have　been　studied.　The　results　show　that　the　simulation　results　agree　well　with　experimental　results.　There　exist　complex　vortex　structures　in　oil　cavity.　The　vortices　number　varies　from　one　to　three　and　the　vortices　size　and　positions　change　as　Re　(70~1400)　increases.　The　vortices　size　increases　and　vortices　number　decreases　as　H　varies　from　6mm　to　18mm.　As　h　increases,　the　vortices　size　increases　obviously.　The　wall　pressure　and　shear　stress　increase　as　Re　increases　and　h　decreases　in　the　same　conditions.　The　results　provide　a　foundation　for　improving　the　stability　and　carrying　capacity　of　hydrostatic　oil　cavity.　©,　2015,　Tsinghua　University.　All　right　reserved.