Abstarct: Many buildings in seismic zones have been baxsed on existing seismic regulations are inappropriate. In addition, the number of major earthquakes that have occurred during recent years has made it more important for seismic mitigation. Seismic retrofitting of existing buildings is one of the most effective ways to reduce these risks. There are different methods for seismic rehabilitation of structures, such as the use of steel braces and shear walls and ...., But before choosing a method of strengthening will be a precise estimate of the seismic behavior and performance. Nonlinear static and nonlinear dynamic analysis method are appropriate methods for determining the seismic performance of structures. In addition analyses, damage indexes can also be helpful in determining the structural condition and amount of damage in structure. Damage indexes in fact, a mathematical model to describe the quality and quantity of structures in probable earthquakes. In this study three steel moment frxame with 5, 7 and 10 story rehabilitated by using different types of bracing systems, to determine the effectiveness and performance of the various methods of retrofitting, nonlinear static and dynamic analyses were performed by using perform 3d software and baxsed on "Ghobarah" damage index that set baxsed on resistance parameter, structural damage rate was calculated before and after retrofitting. Results indicate that the EBF braced system has a better efficacity on retrofitting of the structure.