Abstract: Based on the conclusion that the duality principle of complex boundary-value problems of electromagnetic fields, the PO algorithm architecture for an anisotropic medium coating target under arbitrary electromagnetic current source excitation is described in this paper, meanwhile, the two types of spectral-domain DGFs for electric and magnetic excitation sources and the spatial characteristic analysis are derived. Based on the spectral-domain asymptotic solution of the infinite PEC plane coated with the anisotropic medium under arbitrary source excitation. Firstly, the outer surface of a complex target is discretized into countless planar triangular facets. Secondly, based on the tangent plane approximation principle, the surface scattering field of an individual tiny facet can be equivalent to the scattering field of an anisotropic-medium-coated infinite PEC plane. After obtaining the equivalent electromagnetic currents (EECs) on the facet surface, then the PO solutions of all illuminated surface facets are further superimposed to solve the total scattering field. The scattered field solution in the paper is proved to be reasonable and credible by comparing it with the results of the EM simulation software algorithm.