Abstarct: In the past, in analysis of structures, analysis and design process tended to consider the soil and structure in relative isolation. If the structure made on stiff rocks, this assumption is correct. Today, in design of super-structures , the engineers consider the effect of interaction between soil and structure to avoid damages such as separation of structure from foundation or sudden failure. One of the structures subjected to the effect of soil-structure interaction are bridge piers located on the soft soil. Usually in this situation use single pile rarely and group of piles mostly. In this thesis first of all we try to investigate the effect of soil-structure interaction in single pile in different loading , then we demonstrate the effect of soil-structure interaction in group of piles. For analysis of our numerical problems we use Finite Element Method (FEM) and for this process we use ABAQUS which is a commercial software. Results of analysis in this thesis display that the effect of interaction between soil and single pile under static loads, does not affect on the magnitude of displacements and maximum principal stresses. But in dynamic loads soil-pile interaction will reduce displacements and maximum principal stresses.