Abstract: The calculation formulas of monostatic radar cross-section (RCS) of arbitrary reflectors with arbitrarily polarized plane-wave incidence are derived, where the specular field is obtained by geometrical optics and the edge-diffracted field is calculated by the method of equivalent currents (MEC). Some typical results calculated are given by means of RCS spatial graphs. For both horizontal and vertical polarizations, the theoretical results obtained in this paper agree very well with the experimental results as well as the results from uniform theory of diffraction.