2D spectral elements are employed to discretize the cross section of a layered structure,the structure is divided into several substructures homogeneous along the longitudinal direction .A Riccati equationbased high precision integration (HPI) method is utilized to perform integration along the the longitudinal direction, which is the undiscretized direction, to generate the stiffness matrix of the whole layered structure. The spectral element can avoid the well-known Runge phenomenon and achieve spectral accuracy, which means the numerical results can converge exponentially as the increase of interpolation order of basis functions.Numerical examples demonstrate the high efficiency and accuracy of the proposed method.Genetic Algorithm is used to optimize PBG structure based on the Semi-Analytical Spectral Element Method.