Abstract: The linear bending of symmet ric laminates was analysed，which are composed of unidirectional materials and interleaved viscoelastic damping layer. The viscoelastic layer was treated as isotropic materials. The strain energy stored in in-plane as well as in transverse shear was considered. The Ritz method was employed to research the strain energy of individual stress components. As an example，for a square plate with the boundary condition of four edges clamped，the individual stress components and their strain energy of the unidirectional materials and the viscoelastic layers as well as the loss factor of the composite structures were discussed. The results show that the total energy is mainly composed of the in-plane strain energy in the composites and the shear strain energy in xz and yz directions in the viscoelastic damping layer. The disparity in Young‘s modulus between the viscoelastic damping layer and the unidirectional materials momentously impact the loss factor of the composite structures.