Based　on　the　FLOEFD　analysis　and　the　indoor　experiment　tests,　the　characteristic　of　valve　internal　leakage　under　different　transfer　pressure　have　been　studied.　It　is　found　that　the　oil　which　leaked　from　the　center　of　the　hole　has　the　highest　velocity　and　after　leakage,　the　oil　velocity　first　increased　and　then　decreased.　The　leakage　velocity　peak　value　increased　with　the　increase　of　the　transfer　pressure　and　decrease　of　leakage　area.　The　mass　flow　of　the　oil　leaked　through　the　smallest　hole　is　the　smallest　and　it　increased　with　the　increase　of　the　transfer　pressure.