The　nonlinear　vibrations　of　two　flexible　cantilever　beams　with　different　sections,　which　are　subjected　to　harmonic　vertical　base　excitation,　are　studied　experimentally.　The　periodic　motions　and　chaotic　motions　are　demonstrated.　And　the　multi-pulse　orbits,　which　imply　the　existence　of　chaos　under　the　Smale　horseshoes　sense,　are　also　observed.