In　order　to　study　the　cavitation　fuel　flow　characteristics　inside　the　diesel　nozzle,　based　on　the　same　cavitation　number　and　the　similar　structure　of　the　baseline　nozzle,　the　flow　characteristics　of　the　nozzle　were　tested　on　the　optical　test　rig,　together　with　the　CFD　three-dimensional　simulation.　An　investigation　on　the　characteristics　at　the　nozzle　outlet　during　the　cavitation　period,　and　the　influence　of　cavitation　on　the　flow　characteristics　such　as　the　velocity,　the　density,　and　the　turbulence　kinetic　energy　were　presented.　The　flow　characteristics　at　the　nozzle　outlet　were　analyzed　as　the　back　pressure　decreased.　The　results　show　that　for　stable　inlet　pressure,　cavitation　at　inlet　cross-section　becomes　first　stronger　and　then　stable　as　the　back　pressure　drops.　At　the　nozzle　outlet,　the　cavitation　and　the　fuel　density　continue　increasing　with　the　decrease　in　the　back　pressure.　The　turbulent　kinetic　energy　constantly　increases　with　back　pressure　decreasing　in　the　nozzle.　However,　the　cavitation　increase　rate　at　saturation　stage　is　less　than　that　of　without　cavitation　and　cavitation　developing　period.　During　the　no　cavitation　stage,　the　liquid　average　velocity　has　no　difference　at　the　inlet　and　outlet　cross-section　of　nozzle,but　the　velocity　difference　between　the　nozzle　inlet　and　the　outlet　increases　during　both　the　cavitation　developing　and　saturation　periods.　©　2018,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.