In electromagnetic transient studies, only a small part of an AC power system can be modeled in detail. The remaining parts of the system should be reduced to equivalent model. This study presents an approach for obtaining network equivalents for ac power systems using QZ algorithm. The proposed method obtains accurate resonant frequencies directly from the system equations to be used in finding the network equivalent parameters. Also, the proposed method is a useful tool to predict the system response and has the following advantages. It has less complexity because it obtains the minima and maxima frequencies directly from the system equations. It gives reliable prediction and complete information about behavior of the test system and its peaks and troughs before calculating its frequency response. The proposed method determines the accurate value for resistors of the network equivalent model as the real part of the impedance function magnitude at the minima frequency points. In this study, a general algorithm is developed to determine the frequency dependent network equivalent model parameters for any given system. Finally, this method is implemented on Hormozgan network as a part of Iran electric power network and the parameters of equivalent circuit are calculated.