In this paper the progressive collapse resisting capacity of steel moment frames with MR dampers was evaluated. Parametric studies were carried out using a steel beam-column sub-assemblage with varying natural period and yield strength. The effect of dampers with varying damping coefficients installed in the sub-assemblage was evaluated after sudden removal of the column. Then the progressive collapse potential of a 15-story steel moment frame installed with MR dampers was evaluated by nonlinear dynamic analysis. According to the parametric study the vertical displacement generally decreased as the friction force of MR damper increased, and the dampers were effective both in elastic and elasto-plastic systems. The nonlinear dynamic analysis results of the 15-story analysis models showed that the decrease in vertical deflection of the structure with 9m span length, which showed larger deflection, was more predominant than that of the structure with 6m span length.