About application of Tuned mass dampers (TMDs) on linear structures extensive researches have been done, while studies about TMD application on nonlinear structures are limited and have been based on some simplified assumptions on structure behavior or TMD design procedure. Hence, in this paper it has been decided to study the modeling of TMD on nonlinear structures using the real behavior for structure, and also to assess its effectiveness in improving the seismic behavior of structures. To this end, 3,9 and 20 stories two dimensional steel frames equipped with TMD have been analyzed using OpenSees software under both near-field and far-field earthquakes. For different values of TMD mass ratio, the reduction in controlled structures response such as maximum drift, root-mean-square (RMS) of drift and hysteretic energy has been determined. Results show OpenSees software high ability in modeling the nonlinear structure-TMD system. Based on numerical simulations, it has been found that the effectiveness of TMD in reducing the damage of nonlinear steel frames depends on earthquake characteristics such as frequency content and peak ground acceleration (PGA) as well as TMD mass ratio. Also in this paper a method based on sensitivity analysis has been proposed to determine the parameters of TMD to achieve the better performance in utilizing TMDs on nonlinear structures.