One of the methods for improving the seismic behavior of the moment resisting frames is the using of reduced beam section (RBS) dog-bone connections. In this paper the finite element models of RBS doge-bone connections is made and calibrated to experimental results, the collapse mechanism and stress distribution of these connections is discussed. Moreover, Fema recommendation is considered. This study has been done through the detailed numerical analyses of several samples of these systems. For expressing the advantages of this system, the seismic parameters of RBS dog-bone frames have been compared with those of special moment resisting frames, which are obtained based on several analyses for some common buildings with both connections. Based on the obtained results, the behavior factor of structure is a function of its first fundamental period and increases with period. The increasing rate of the behavior factor of the dog-bone connection system in terms of period is more than that of the special moment resisting frames. The behavior factor of the flexible structures with dog-bone connections is about 20% larger than that of these structures without dog-bone connections. The investigation of ordinary beam to column connections in steel structures shows that non steady stress distribution and stress centralization in welded zone causes the connection fail in strange earthquakes. In RBS dog bone connections the proportion of maximum stress in beam flange to yield stress is about 0.8. The usage of RBS system occasions stress redistribution in beam flange, increasing the effect beam flange width and increasing the connection ductility. In corporation between ordinary and RBS dog bone connections shows the increasing the period of structure about 3 percent. In elastic step, tendency of RBS and ordinary connection system is same but in plastic step the resistance reduction coefficient of RBS system is more about 23 percent than ordinary connection system. This shows the structures that made by RBS systems, have more energy attraction capacity.