Connections have a significant effect on the energy depletion of the structure and its behavior against unusual loads, which often lead to the phenomenon of progressive deterioration; therefore, the study of the effect of mechanical and geometric properties change on connections in steel moment frames against progressive failure in this research. In this regard, the variable parameters include the beam - column connection type (welded flange plate connection or WFP and welded unreinforced flange-welded web connection or WUF-W, reduce beam section connection or RBS, free flange connection FF), the type of steel used at the beam - column connection (St37 and Steel LY 160) and the column removal location in different stories (without removing and removing columns on the ground, first and second stories). Investigations on a three-storey steel frame using ABAQUS finite element software and alternative loads path method. Validation of numerical method was performed using numerical simulation of a steel frame and a suitable agreement was observed. The most important results show that in the frames which low-yielding steel is used at the connection point, the best performance from the demand-to-capacity ratio (DCR) of the beams around removal location belongs to the Free Flange and WUF-W connection frames.