Abstract: For symmetrical composite laminated plates including the coupling of bending and twisting with the simply supported or clamped boundary conditions, an identification theory is presented in this paper to assess the five bending rigidities from the modal analysis of vibration. In the present method the vibration mode of the plate is first obtained approximately from the deflections on the finite measured points in the modal test Then, the bending rigidities of the plate are obtained from the leastsquares method. In the numerical examples, the bending rigidities in three kinds of symmetrical composite laminates under two kinds of boundary conditions are identified using the proposed method. The effect of an important factor on the identification of the bending rigidities, i.e. the number of the measured points for vibration mode, is investigated in detail.