Based　on　wings　flutter　on　flying　aircraft　in　this　paper,　the　authors　study　the　mechanical　model　of　the　rectangular　symmetric　cross-ply　composite　laminated　plates.　Frist,　the　method　of　multiple　scales　is　employed　to　obtain　the　four-dimensional　averaged　equations　of　the　model.　Then,　the　method　of　new　grading　function　and　multiple　Lie　brackets　is　utilized　to　obtain　the　hypernormal　form　(simplest　normal　form,　unique　normal　form)　at　cubic　of　above　averaged　equations.