Abstarct: Progressive collapse is a disastrous phenomenon in structures that can happen due to natural accident or human factors. In progressive collapse the sudden failure of a single element collapse may cause considerable deformations that lead to the destruction of whole structure .Hence analysis of structures against this phenomenon is necessary.. The purpose of this study is to analysis the resistance of steel structures with intermediate moment frxame against the progressive collapse phenomenon in the two conditions , i.e. omitting corner or middle column .This analysis is baxsed on DOD2005 and GSA2003 codes through using the method of alternate load path method .To do this , nonlinear static and dynamic procedures on three dimentional models is carried out by using the SAP2000 software . In dynamic analysis the subject of deleting middle and corner columns in very short time(0.0025,0.005,0.01) is studied , and the effect of the number of stories ,length and height of bays on progressive collapse mechanism is evaluated. The analysis include target point maximum displacement, plastic hinges creation , the amount of maximum positive and negative moments of beams in damaged bays. Also displacement fluctuations of target point due to instantaneous removal of column is investigated.