The　fuel　flow　in　the　working　chamber　of　the　common　rail　fuel　injector,　which　is　a　submerged　jet　flow,　determines　the　needle　movement　and　causes　great　effects　on　the　fuel　injection　performance.　This　work　presents　an　experimental　investigation　on　the　submerged　jet　flow　characteristics　of　a　cylindrical　orifice　under　conditions　of　varied　boundary　pressures.　A　full-scale　optical　test　rig　is　set　up　to　examine　the　submerged　flow　of　the　cylindrical　orifice　based　on　a　fuel　pump　test　bench.　The　optical　experimental　results　reveal　that　the　inner　cylindrical　orifice　flow　induces　cavitation　and　causes　influences　on　the　submerged　jet　flow.　As　the　inner　cavitation　is　at　the　cylindrical　orifice　outlet,　the　cylindrical　orifice　discharge　coefficient　declines　but　the　mass　flow　rate　becomes　choking.　The　test　results　also　show　the　boundary　pressures　(the　inlet　and　outlet　pressures)　of　the　cylindrical　orifice　have　great　influences　on　the　impingement　force　of　the　submerged　jet　flow.　The　development　process　of　the　impingement　force　is　divided　into　two　periods:　the　stable　period　and　the　fluctuation　period.　Moreover,　the　impingement　force　increases　quadratically　with　the　increase　in　the　mass　flow　rate.　Once　the　choking　flow　happens,　it　is　useless　to　increase　the　jet　impingement　force　by　improving　the　inlet　pressure.