1. A computer system, comprising: a central processing unit; a storage device storing one or more programs, the one or more programs comprising: an acquisition module configured for reading a data file corresponding to a W-element format in the storage device, wherein the W-element is a transmission line model in HSPICE, and obtain a frequency-dependent transmission matrix from the data file using an interpolation algorithm; a first parameter transformation module configured for transforming the frequency-dependent transmission matrix into an N-port network matrix, wherein the N-port network matrix describes electrical properties of a multi-input and multi-output network; a second parameter transformation module configured for transforming the N-port network matrix into a S-parameter matrix; a parameter determination module configured for determining a range of frequency of a S-parameter in the S-parameter matrix, and for determining numbers of pole-residue, a number of recursion of a vector fitting occurs, and durable maximum system errors in an equivalent circuit simulation; and an equivalent circuit production module configured for performing a vector fitting algorithm, producing a rational function matrix composed with the S-parameters, wherein the rational function matrix comprises function for determining the S-parameters in the S-parameter matrix, and producing an equivalent circuit compatible with HSPICE format based on the generated rational function matrix.