The　global　bifurcations　and　multi-pulse　chaotic　dynamics　of　the　four-edge　simply　supported　rectangular　thin　plate　under　in-plane　excitation　are　investigated.　Based　on　the　von　Karman　theory　and　the　Reddy＇s　high-order　shear　deformation　theory,　the　formulas　of　motion　for　the　four-edge　simply　supported　rectangular　thin　plate　subjected　to　the　in-plane　excitation　are　derived.　Then　the　Galerkin　method　is　employed　to　discrete　the　partial　differential　equations.　The　non-autonomous　ordinary　differential　equations　with　three-degree-of-freedom　are　derived　by　using　this　method.　The　extended　Melnikov　method　is　improved　to　investigate　the　six-dimensional　nonautonomous　nonlinear　dynamical　system　in　mixed　coordinate.　The　multipulse　chaotic　dynamics　of　the　six-dimensional　nonautonomous　rectangular　thin　plate,　which　is　buckled　in　the　first-order　mode,　meanwhile　it　is　not　buckled　in　the　second-order　mode　and　the　third-order　mode,　are　studied　directly　by　using　this　method.　The　three-order　normal　forms　of　the　six-dimensional　nonautonomous　nonlinear　dynamical　equations　are　obtained　by　using　the　theory　of　normal　form.　Then　making　use　of　the　residue　theory,　the　Melnikov　functions　can　be　established.　The　multi-pulse　chaotic　motions　of　the　four-edge　simply　supported　rectangular　thin　plate　are　found　from　the　numerical　simulation　which　further　verifies　the　result　of　theoretical　analysis.　©　2011　IEEE.