The current methods in seismic design of structures include force or displacement based method. Each of these two methods has advantages and disadvantages which the same thing has led the researchers to introduce compound seismic design methods in recent years by combining force and displacement methods. The purpose of this paper is introducing a new combined method called "Modified Earthquake Coefficient Method". This method is derived from the combination of the force method of the fourth edition of the Iranian seismic code (Standard no.2800) and the displacement method presented in the first revision of the instruction for seismic rehabilitation of existing buildings (Publication no.360). In this method, the coefficient of behavior and reflection coefficient are determined by observing the actual behavior of the structure and taking into account the analytic period of the structure. In order to determine the behavior coefficient in this method, nonlinear static analysis (pushover analysis) is using. In order to evaluate the proposed method, moment resisting frames with special ductility were designed in 3, 6 and 9 story frames based the force method of standard 2800 and the proposed method of this paper then their various responses have been compared. The proposed method in 3, 6 and 9 story frames in addition to providing the life safety function at target's displacement respectively reduced 242, 601 and 840 kgf the weight of the frames.