The Northridge earthquake on 1994 was a turning point in the design of rigid beam to column connection and revealed some major weaknesses in those types of connections that were being implemented in that time. Connection with side plates is a kind of improved connection which was proposed after the earthquake and can lead to healing those major weaknesses. According to the experiments it was observed that during the loading as a result of stress concentration the beam flange and its welds that are close to the side plate are the starting point to crack and failure. In this research in order to overcome these weaknesses, a new method has been proposed and new parts have been modeled and nonlinearly analyzed both materially and geometrically using programming in Ansys software. Also in order to validate the results obtained from modeling an experimental work has been done to backup the conclusion. The results verify that the new shape of connection would overcome the existing weaknesses as well as increasing strength capacity and better performance of the connection is achieved. According the results the experimented connection is accounted as a connection of special moment frame (SMF).