To　study　the　cavitation　occurring　in　diesel　nozzle　and　its　effects　on　the　flow　capacity,　the　process　of　cavitation　and　the　flow　characteristics　in　diesel　injector　orifice　were　analyzed　based　on　optical　testing　and　three-dimensional　CFD　simulation.　In　the　experiment,　the　visualization　of　cavitation　was　recorded　by　a　high-speed　camera,　the　frame　rate　was　set　to　6　688　frames　per　second.　The　high-frequency　Kistler　pressure　transducers　were　assembled　before　and　after　the　nozzle　to　acquire　pressure.　Ultimately,　the　data　of　pictures　and　pressure　were　stored　by　a　computer.　The　3D　CFD　diesel　cavitation　simulations　were　carried　out　under　conditions　of　different　inlet　pressures　and　back　pressures　based　on　the　commercial　code　Fluent.　The　CFD　simulations　were　validated　by　the　experimental　data.　The　results　showed　that:　when　K＞2.49,　there　were　no　bubbles　in　the　nozzle,　which　was　named　no-cavitation　period;　during　no-cavitation　period,　both　the　gas-liquid　mixed　phase　volume　fraction　and　the　fuel　mass　flow　in　each　section　did　not　increase　and　the　flow　coefficient　was　constant.　When　K≤2.49,　it　is　the　cavitation　developing　period　when　the　gas-liquid　mixed　phase　volume　fraction　of　the　entrance　of　the　nozzle　(plane　A)　started　to　increase　which　represented　cavitation　inception.　At　the　same　time,　the　growth　rate　of　fuel　mass　flow　reduced,　and　the　flow　coefficient　began　to　decreased.　When　K≤1.91,　the　gas-liquid　mixed　phase　volume　at　plane　A　became　stable,　which　meant　the　cavitation　saturation　period.　During　the　saturation　period,　the　fuel　mass　flow　rised　to　its　maximum　and　maintained　stable　while　the　flow　coefficient　decreased.　It　can　be　seen　that　the　cavitation　occurred　in　diesel　injector　nozzle　had　large　impact　on　the　flow　characteristics.　Meanwhile,　the　cavitation　had　impact　on　the　fuel　mass　flow,　the　flow　coefficient　and　the　gas-liquid　mixing　phase　volume　fraction　at　different　nozzle　cross　sections.　©　2016,　Chinese　Society　of　Agricultural　Machinery.　All　right　reserved.