This paper uses the multi-purpose software ABAQUS to create a three-dimensional finite element model of an extended end plate connection to analyze and compare the behaviour of mild steel and high-strength steel endplate connections. The numerical model's results are calibrated against reported experimental results to ensure that it can simulate and analyze both the overall and detailed behaviour of different types of bolted endplate steel connections. The results of the study compare and analyze the moment-rotation relationships and the behaviour characteristics of the connection with mild steel and high strength steel. Upon validation of the FE models' parametric studies were performed to investigate the effect of different parameters on the behavior of bolted extended end-plate connection. Therefore, the geometric parameters are selected and varied within the comprehensive practical ranges of extended end-plate connections.The parameters varied for the parametric studies include the thickness of the end plate, bolt diameter and steel grade of the endplate.