Abstract: As laminated composite plates have relatively low transverse shear modulus, Kirchhoff theory has been proved to be inadequate for calculating the eigenvalues and their sensitivity in laminated plates.A first-order shear deformation theory is used for symmetrically laminated plates in the paper. The orientation angle of fibres, the material parameter and the vertical distance from the middle plane of the laminated plates of the upper surface of each ply are treated as design variables, and the sensitivity of eigenvalues for the symmetrically laminated plates is studied.