Perturbation　analysis　and　chaotic　dynamics　of　the　rotating　blade　with　varying　angular　speed　are　investigated.　Centrifugal　force,　aerodynamic　load　and　the　perturbed　angular　speed　due　to　the　inconstant　air　velocity　are　considered.　The　rotating　blade　is　treated　as　a　pre-twist,　presetting,　thin-walled　rotating　cantilever　beam.　The　nonlinear　governing　partial　differential　equations　of　the　varying　angular　rotating　blade　are　established　by　using　Hamilton＇s　principle.　Then,　the　ordinary　differential　equations　of　the　rotating　blade　are　obtained　by　employing　the　Galerkin＇s　approach　during　which　Galerkin＇s　modes　satisfy　corresponding　boundary　conditions.　The　four-dimensional　nonlinear　averaged　equations　are　obtained　by　applying　the　method　of　multiple　scales.　In　this　paper,　the　resonant　case　is　1:2　internal　resonance-1/2　subharmonic　resonance.　The　numerical　simulation　is　used　to　investigate　chaotic　dynamics　of　the　varying　angular　rotating　blade.　The　results　show　that　the　system　is　sensitive　to　the　rotating　speed　and　there　are　chaotic　motions.　Copyright　©　2011　by　ASME.