Passive　vibration　isolation　techniques　with　low-frequency　characteristics　have　been　a　hot　topic　in　the　aerospace　field.　A　hydraulic　inertial　vibration　isolator　is　a　highly　effective　type　of　isolator　for　controlling　low-frequency　vibrations.　It　typically　consists　of　a　main　spring,　a　minor　spring,　an　inertial　mass,　and　a　fluid　domain.　Due　to　its　multi-domain　nature,　analyzing　the　isolation　mechanism　of　this　type　of　isolator　is　challenging.　The　bond　graph　method　is　employed　to　establish　the　dynamic　model　of　the　isolator.　Subsequently,　the　state　equations　of　the　isolator　are　derived,　and　the　energy　equations　of　both　the　mechanical　and　the　fluid　parts　of　the　isolator　are　obtained.　Based　on　this,　the　energy　transfer　characteristics　between　the　mechanical　and　fluid　domains　inside　the　isolator　under　external　excitation　are　discussed.　The　time-domain　response　of　the　forces　transmitted　to　the　foundation　is　analyzed.　It　is　shown　that　the　anti-resonance　frequency　occurs　when　the　forces　transmitted　to　the　foundation　generated　by　the　main　spring　and　the　fluid　pressure　are　equal　to　that　of　the　minor　spring.　To　verify　the　proposed　method’s　correctness,　a　prototype　of　the　isolator　is　designed　and　a　carefully　designed　experiment　is　conducted.　The　acceleration　transmissibility　of　the　isolator　is　used　to　conduct　a　comparative　study.　The　results　show　that　the　theoretical　results　are　in　good　agreement　with　the　experimental　results.　To　depict　the　dynamic　characteristics　of　the　isolator　under　large　amplitude　vibration,　the　nonlinear　dynamic　model　of　the　isolator　is　developed,　and　the　corresponding　force　transmissibility　of　the　isolator　is　formulated.　The　energy　flow　between　the　mechanical　and　the　fluid　domains　under　this　condition　is　also　analyzed.　The　results　indicate　that　the　energy　flow　responses　exhibit　a　similar　change　tendency　to　the　force　transmissibility.　However,　the　peak　of　the　energy　ratio　between　the　mechanical　subsystem　and　the　fluid　is　the　same　as　the　linear　condition,　suggesting　that　this　value　is　determined　by　the　amplification　ratio　of　the　isolator.　This　research　provides　enhanced　physical　insight　to　understand　the　dynamic　characteristics　of　this　type　of　isolator　and　will　help　to　shorten　the　design　cycle　of　the　isolator.　©　2024　by　the　authors.