Nonlinear　vibrations　of　carbon　fiber　reinforced　composite　sandwich　plate　with　pyramidal　truss　core　are　investigated.　The　governing　equation　of　motion　for　the　sandwich　plate　is　derived　by　using　a　Zig-Zag　theory　under　consideration　of　geometrically　nonlinear.　The　natural　frequencies　of　sandwich　plates　with　different　dimensions　are　calculated　and　compared　with　those　obtained　from　the　classic　laminated　plate　theory　and　Reddy＇s　third-order　shear　deformation　plate　theory.　The　frequency　responses　and　waveforms　of　the　sandwich　plate　when　1:3　internal　resonance　occurs　are　obtained,　and　the　characteristics　of　the　internal　resonance　are　discussed.　The　influences　of　layer　number　of　face　sheet,　strut　radius,　core　height　and　inclination　angle　on　the　nonlinear　responses　of　the　sandwich　plate　are　analyzed.　The　results　demonstrate　that　the　strut　radius　and　inclination　angle　mainly　affect　the　resonance　frequency　band　of　the　sandwich　plate,　and　the　layer　number　and　core　height　not　only　influence　the　resonance　frequency　band　but　also　significantly　affect　the　response　amplitude.