An efficient reduced model of the method of moments based on the second-order Arnoldi (SOAR) algorithm is proposed for the wide-band simulations of the microstrip circuits. In order to construct the reduced model, the second-order Taylor series is employed to expand the impedance matrix, and then the impedance matrix can be linearised with respect to the frequency with transformations. Thus a (SOAR) algorithm can be used to obtain the reduced model, which preserves the characteristics of the original model with predetermined error. The solutions of the reduced model can be obtained effectively at each frequency, and the surface currents of the original model can be obtained with a simple projection, thus the wideband interested parameters can be extracted.