In　this　paper,　research　on　nonlinear　dynamic　behavior　of　a　string-beam　coupled　system　subjected　to　parametric　and　external　excitations　is　presented.　The　governing　equations　of　motion　are　obtained　for　the　nonlinear　transverse　vibrations　of　the　string-beam　coupled　system.　The　Galerkin＇s　method　is　employed　to　simplify　the　governing　equations　to　a　set　of　ordinary　differential　equations　with　two　degrees-of-freedom.　The　case　of　1:2　internal　resonance　between　the　modes　of　the　beam　and　string,　principal　parametric　resonance　for　the　beam,　and　primary　resonance　for　the　string　is　considered.　The　method　of　multiple　scales　is　utilized　to　analyze　the　nonlinear　responses　of　the　string-beam　coupled　system.　Based　on　the　averaged　equation　obtained　here,　the　techniques　of　phase　portrait,　waveform,　and　Poincare　map　are　applied　to　analyze　the　periodic　and　chaotic　motions.　It　is　found　from　numerical　simulations　that　there　are　obvious　jumping　phenomena　in　the　resonant　response-frequency　curves.　It　is　indicated　from　the　phase　portrait　and　Poincare　map　that　period-4,　period-2,　and　periodic　solutions　and　chaotic　motions　occur　in　the　transverse　nonlinear　vibrations　of　the　string-beam　coupled　system　under　certain　conditions.