Analysis　on　nonlinear　dynamics　behavior　of　a　string-beam　coupled　system　subjected　to　a　harmonic　axial　load　is　presented.　The　nonlinear　governing　equations　of　motion　are　obtained　for　the　string-beam　coupled　system.　The　governing　equations　are　discretized　to　a　four-degree-of-freedom　nonlinear　system　by　using　the　Galerkin＇s　method.　The　method　of　multiple　scales　is　utilized　to　obtain　the　eight-dimensional　averaged　equations.　Using　numerical　method,　the　averaged　equations　are　analyzed　to　obtain　the　resonant　response-frequency　curves.　Under　certain　conditions　the　quasi-periodic　solutions　and　chaotic　motions　of　the　string-beam　coupled　system　are　found.　It　is　found　that　there　exist　different　kinds　of　chaotic　motions　in　the　string-beam　coupled　system.