1. A computer implemented method for making a simplified circuit model comprising: using said computer to perform the steps of; (A) inputting a mesh circuit and values of parameters of the mesh circuit; (B) establishing a state matrix of an original circuit mode; (C) inputting an order of a simplified circuit and acquiring a corresponding orthonormal matrix by an adaptive-order multipoint rational Arnoldi algorithm, wherein the adaptive-order multipoint rational Arnoldi algorithm consists of: (a) Approximation model using moment matching method; (b) Arnoldi algorithm that features Krylov subspace iteration; (c) An approximation model that contains several expansion frequencies; and (d) An expansion frequency selection methods; (D) orthogonally projecting the state matrix of the original circuit mode into the corresponding orthonormal matrix of the simplified circuit; (E) outputting the simplified circuit model from the orthogonally projection; and (F) storing the simplified circuit model in the computer memory.