Global　dynamics　of　a　flexible　asymmetrical　rotor　resting　on　vibrating　supports　is　investigated.　Hamilton＇s　principle　is　used　to　derive　the　partial　differential　governing　equations　of　the　rotor　system.　The　equations　are　then　transformed　into　a　discretized　nonlinear　gyroscopic　system　via　Galerkin＇s　method.　The　canonical　transformation　and　normal　form　theory　are　applied　to　reduce　the　system　to　the　near-integrable　Hamiltonian　standard　forms　considering　zero-to-one　internal　resonance.　The　energy-phase　method　is　employed　to　study　the　chaotic　dynamics　by　identifying　the　existence　of　multi-pulse　jumping　orbits　in　the　perturbed　phase　space.　In　both　the　Hamiltonian　and　the　dissipative　perturbation,　the　homoclinic　trees　which　describe　the　repeated　bifurcations　of　multi-pulse　solutions　are　demonstrated.　In　the　case　of　damping　dissipative　perturbation,　the　existence　of　generalized　ilnikov-type　multi-pulse　orbits　which　are　homoclinic　to　fixed　points　on　the　slow　manifold　is　examined　and　the　parameter　region　for　which　the　dynamical　system　may　exhibit　chaotic　motions　in　the　sense　of　Smale　horseshoes　is　obtained　analytically.　The　global　results　are　finally　interpreted　in　terms　of　the　physical　motion　of　axis　orbit.　The　present　study　indicates　that　the　existence　of　multi-pulse　homoclinic　orbits　provides　a　mechanism　for　how　energy　may　flow　from　the　high-frequency　mode　to　the　low-frequency　mode　when　the　rotor　system　operates　near　the　first-order　critical　speed.