Abstract:To investigate the problem of classical analytical method, which can not be used at Low-Grazing Angle (LGA) for rough surface scattering, a new high-order analytical method based on the high-order series expansion of the two-dimensional electric field and the profile function of rough surface is adopted. By this arithmetic, the co-polarized backscattering coefficient at LGA is compared with high-order Small Perturbation Method (SPM) and classical SPM, the grazing effect at different roughness is discussed, the modified effect for Gaussian rough surface at LGA is analyzed by high-order SPM and high-order Kirchhoff Approximation (KA). The result shows that the high-order analytical method is valid for LGA problem. At last,the vertical-to-horizontal Polarization Ratio (PR) with different power of secant function of grazing incident angle and scattering angle is considered particularly, and the classical expression of PR is rectified.