Inthispaper,fundamentalequationsandboundaryconditionsofthenonlinearbendingtheoryforarectangularsandwiclplatewithasoftcorearederivedbymeansofthemethodofcalculusofvariations.Thenthenonlinearbendingforasimplysupportedrectangularsandwichplateundertheuniformlateralloadisinvestigatedbyuseoftheperturbationmethodandaquiteaccurateanalyticsolutionisobtained.