Global　bifurcations　and　multi-pulse　chaotic　dynamics　for　a　simply　supported　rectangular　thin　plate　are　studied　by　the　extended　Melnikov　method.　The　rectangular　thin　plate　is　subject　to　transversal　and　in-plane　excitation.　A　two-degree-of-freedom　nonlinear　nonautonomous　system　governing　equations　of　motion　for　the　rectangular　thin　plate　is　derived　by　the　von　Karman　type　equation　and　the　Galerkin　approach.　A　one-toone　internal　resonance　is　considered.　An　averaged　equation　is　obtained　with　a　multi-scale　method.　After　transforming　the　averaged　equation　into　a　standard　form,　the　extended　Melnikov　method　is　used　to　show　the　existence　of　multi-pulse　chaotic　dynamics,　which　can　be　used　to　explain　the　mechanism　of　modal　interactions　of　thin　plates.　A　method　for　calculating　the　Melnikov　function　is　given　without　an　explicit　analytical　expression　of　homoclinic　orbits.　Furthermore,　restrictions　on　the　damping,　excitation,　and　detuning　parameters　are　obtained,　under　which　the　multi-pulse　chaotic　dynamics　is　expected.　The　results　of　numerical　simulations　are　also　given　to　indicate　the　existence　of　small　amplitude　multi-pulse　chaotic　responses　for　the　rectangular　thin　plate.