Abstract: The present paper provides a theoretical proof for that the natural frepuency of laminated plate under lateral load can be reduced and the deflection of the plate increased by the coupling between bending and extension.The expressions of the natural frequency and deflection under lateral load for laminates have been derived.It is proved that the expressions of both the natural frequency and the deflection consist of two terms.The first term which is as the same as corresponding expression of symmetrical laminate is positive and the second term negative,which is the influence of the coupling between beetling and extension.The laminates which give the highest natural freuluencv and the lowowest deflection are found to he symmetrical laminates from optimum analysis of laminates.