The　cavitation　erosion　behavior　of　Cr32Ni7Mo3N　hyper　duplex　stainless　steel　in　both　distilled　water　and　artificial　seawater　was　investigated　by　a　magnetostrictive-induced　cavitation　facility.　The　micrographs　of　damaged　surfaces　after　cavitation　for　different　intervals　of　time　were　observed　by　scanning　electron　microscopy　(SEM).　The　cumulative　mass　loss　curves　and　cumulative　mass　loss　rate　curves　of　specimens　were　drawn　by　measuring　the　weight　loss.　The　polarization　curves　and　free-corrosion　potentials　of　specimens　were　measured　by　electrochemical　workstation　in　the　static　state　and　in　the　cavitation　erosion　condition.　A　comparison　of　cavitation　erosion　resistance　was　performed　between　the　material　and　SAF2205　steel　in　artificial　seawater.　The　results　show　that　cavitation　damage　firstly　occurs　in　the　ferrite　weak　areas　and　ferrite-austenite　phase　boundaries,　then　gradually　expands　to　the　ferrite　phase,　and　the　ferrite　phase　dissociates　off　at　last.　Its　failure　mode　is　cleavage　brittle　fracture.　As　the　cavitation　erosion　time　prolongs,　the　austenite　phase　microhardness　value　increases　because　of　slip　lines　generating　more.　During　the　entire　cavitation,　the　microhardness　value　of　the　austenite　phase　in　artificial　seawater　is　higher　than　that　in　distilled　water.　When　the　ferrite　phase　is　largely　destroyed,　austenite　phase　damage　begins　to　happen　and　drop　off.　Its　failure　mode　is　ductile　failure.　So　the　existence　of　austenite　delays　fracture　expanding　to　the　entire　material　surface.　In　artificial　seawater,　the　interaction　of　both　cavitation　erosion　and　corrosion　leads　to　material　failure　acceleration,　and　the　cavitation　erosion　resistance　of　Cr32Ni7Mo3N　steel　is　better　than　that　of　SAF2205　steel.