In　this　study,　the　nonlinear　vibrations　of　an　axially　moving　beam　are　investigated　by　considering　the　coupling　of　the　longitudinal　and　transversal　motion.　The　Galerkin　method　is　used　to　truncate　the　governing　partial　differential　equations　into　a　set　of　coupled　nonlinear　ordinary　differential　equations.　By　detuning　the　axially　velocity,　the　exact　parameters　with　which　the　system　may　turn　to　internal　resonance　are　detected.　The　method　of　multiple　scales　is　applied　to　the　governing　equations　to　study　the　nonlinear　dynamics　of　the　steady-state　response　caused　by　the　internal-external　resonance.　The　saturation　and　jump　phenomena　of　such　system　have　been　reported　by　investigating　the　nonlinear　amplitude-response　curves　with　respect　to　external　excitation,　internal,　and　external　detuning　parameters.　The　longitudinal　external　excitation　may　trigger　only　longitudinal　response　when　excitation　amplitude　is　weak.　However,　beyond　the　critical　excitation　amplitude,　the　response　energy　will　be　transferred　from　the　longitudinal　motion　to　the　transversal　motion　even　the　excitation　is　employed　on　the　longitudinal　direction.　Such　energy　transfer　due　to　saturation　has　the　potential　to　be　used　in　the　vibration　suppression.